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A Diamond Is Forever | History and myths | "A Diamond Is Forever" is the De Beers advertising slogan written by copywriter Frances Gerety in 1947, later named by Advertising Age the top advertising slogan of the twentieth century. | The line was written by Frances Gerety, a copywriter at the Philadelphia agency N.W. Ayer, in 1947, for the De Beers account. In 1999, Advertising Age named it the number one advertising slogan of the twentieth century. Its staying power comes from a simple pairing: a diamond is the hardest natural material, a 10 on th... | [
{
"claim": "The slogan \"A Diamond Is Forever\" was written by copywriter Frances Gerety at the N.W. Ayer agency for De Beers in 1947.",
"source": "Task anchor; N.W. Ayer / De Beers advertising history (Wikipedia, Frances Gerety)",
"date": "1947"
},
{
"claim": "Advertising Age named \"A Diamond ... | [
"The months-of-salary rule",
"The 4Cs",
"Round brilliant cut",
"Engagement ring history",
"Lab Grown Diamonds"
] |
Annual Prong Check | Care and buying | An annual prong check is a yearly appointment where a jeweler inspects the small metal claws holding your diamond and re-tightens or rebuilds any that have worn down. It is the single best habit for not losing a stone. | Prongs are the small metal tips that curl over the edge of a diamond to hold it in place. They take the brunt of daily life: every time a ring bumps a doorknob, a countertop, or a car door, the prongs absorb it. Over months and years that contact wears the metal thin, and a thin prong can bend, snag, or break. When a p... | [] | [
"Prong Setting",
"Cleaning a Diamond Ring at Home",
"Insuring an Engagement Ring",
"Ultrasonic Cleaners",
"Setting Styles"
] |
asscher cut | Cuts and shapes | An Asscher cut is a square step cut with cut corners, essentially a square emerald cut with deeper, more pronounced steps that draw the eye toward the center in an X or windmill pattern. It reads as a nearly octagonal square with concentric squares of light. | The Asscher belongs to the step-cut family, the same family as the emerald cut. Its outline is square rather than rectangular, with the four corners cut off so that it appears almost octagonal. The step facets are usually cut steeper and deeper than an emerald cut's, and the pavilion draws down to a small center, produ... | [] | [
"emerald cut",
"step cut",
"princess cut",
"cushion cut",
"table",
"four Cs"
] |
bezel setting | Settings and metals | A bezel setting surrounds the diamond with a continuous metal rim that grips the stone around its girdle. It is the most protective common setting, covering and cushioning the stone's edges. | In a bezel setting, a thin wall of metal is shaped to follow the outline of the stone and then pressed over the edge so it holds the diamond the way a frame holds a picture. A full bezel encircles the whole stone. Because the rim covers the girdle, the thin outer edge where chips usually start, and sits flush or nearly... | [] | [
"prong setting",
"half bezel",
"girdle",
"solitaire",
"platinum",
"cathedral setting"
] |
bow-tie effect | Diamond anatomy | The bow-tie effect is a dark, bow-tie-shaped shadow across the center of many elongated diamond shapes. It is normal light behavior in these outlines, not a flaw. | The bow-tie effect is a shadow shaped like a bow tie, or two dark triangles meeting point to point, seen across the middle of many elongated diamonds when you look at them face-up. It shows up in ovals, pears, marquises, and elongated hexagonal cuts, among others.
It's a product of geometry, not a defect. In a stretch... | [] | [
"length-to-width ratio",
"pavilion",
"oval cut",
"marquise cut",
"Dutch Marquise"
] |
Brilliance | Light and optics | Brilliance is the brightness a diamond returns to the eye: the white light reflected from its surface and, mostly, from inside the stone after it bounces off the pavilion facets. In GIA's cut model this white light return is called brightness, one of the three components of face-up appearance. | Brilliance has two parts. External brilliance is white light that reflects straight off the surface of the crown facets and the table. Internal brilliance is light that enters the stone, bounces off the pavilion facets by total internal reflection, and returns up through the crown and table to your eye. Most of the bri... | [
{
"claim": "GIA released its round brilliant cut grading system in January 2006; it assesses face-up appearance through brightness (white light return), fire, and scintillation, and assigns a cut grade from Excellent to Poor.",
"source": "GIA (Gemological Institute of America), Diamond Cut grading system, g... | [
"fire (dispersion)",
"scintillation",
"total internal reflection",
"light performance",
"cut grade"
] |
Carat | The 4Cs and grading | A carat is the standard unit of weight for a diamond, equal to exactly 200 milligrams (0.2 grams). It measures weight, not physical size or diameter, and each carat divides into 100 points. | Carat is usually the first C a buyer asks about, because it's the one figure that reads like a headline number. It rewards precise understanding. One metric carat equals exactly 200 milligrams, and jewelers split each carat into 100 points, so a 25-point diamond weighs a quarter of a carat. Don't confuse carat with kar... | [
{
"claim": "The Cullinan is the largest gem-quality rough diamond ever found, at 3,106 carats, recovered in 1905.",
"source": "Gemological Institute of America (GIA)",
"date": "1905"
}
] | [
"the 4Cs",
"cut grade",
"color grade",
"clarity grade",
"round brilliant cut"
] |
cathedral setting | Settings and metals | A cathedral setting supports the center diamond with two arches of metal that sweep up from the band to the stone, like the arches of a cathedral. The arches add height, security, and a graceful profile. | In a cathedral setting, the shoulders of the band do not run straight into the center stone. Instead they rise in curved arches that meet the setting on each side, cradling the stone from below and lifting it up. The name comes from the resemblance to the arched, vaulted architecture of a cathedral. Those arches are st... | [] | [
"solitaire",
"prong setting",
"halo",
"pave",
"bezel setting",
"V-tip prong"
] |
Certification labs | The 4Cs and grading | Certification labs, more precisely gemological grading laboratories, are independent organizations that examine and grade diamonds to published standards. For Lab Grown Diamonds today the main names are GIA, IGI, and GCAL, and the landscape shifted noticeably in 2025 and 2026. | GIA, the Gemological Institute of America, is the nonprofit founded by Robert M. Shipley in 1931 that built the 4Cs framework the whole trade uses. It grades both mined and laboratory-grown stones. On October 1, 2025, GIA moved its Lab Grown Diamond reports to a Premium and Standard tier structure, a change from the le... | [
{
"claim": "GIA (Gemological Institute of America) is a nonprofit founded by Robert M. Shipley in 1931.",
"source": "Gemological Institute of America (GIA)",
"date": "1931"
},
{
"claim": "GIA moved its Lab Grown Diamond reports to Premium and Standard tiers on October 1, 2025.",
"source": "G... | [
"the 4Cs",
"grading report",
"laser inscription",
"cut grade",
"Lab Grown Diamond"
] |
Clarity grade | The 4Cs and grading | A clarity grade rates how free a diamond is of internal inclusions and surface blemishes when examined under 10x magnification, on a scale from Flawless down to Included. It describes tiny features inside and on the stone, most of which the naked eye can't see. | The GIA scale, from best to most included, runs Flawless (FL), Internally Flawless (IF), Very Very Slightly Included (VVS1 and VVS2), Very Slightly Included (VS1 and VS2), Slightly Included (SI1 and SI2), and Included (I1, I2, I3). The reference condition is always 10x magnification: a Flawless diamond shows no inclusi... | [
{
"claim": "IGI still issues full 4C grading reports, including a clarity grade, for Lab Grown Diamonds.",
"source": "International Gemological Institute (IGI)",
"date": "2026"
}
] | [
"the 4Cs",
"eye-clean",
"inclusion",
"laser inscription",
"grading report"
] |
Cleaning a Diamond Ring at Home | Care and buying | You can clean a diamond ring at home with warm water, a little mild dish soap, and a soft brush. Soak it a few minutes, gently brush around and behind the stone, rinse, and pat dry. | A diamond ring picks up a film of hand lotion, soap scum, cooking oils, and skin oil over ordinary wear. Diamond is oleophilic, meaning grease clings to it, so even a spotless-looking stone dulls a little as that film builds. The good news is that removing it is simple and safe to do yourself.
Fill a small bowl with w... | [
{
"claim": "Diamond ranks 10, the maximum, on the Mohs scale of mineral hardness.",
"source": "Mohs scale of mineral hardness (Friedrich Mohs)",
"date": "1812"
}
] | [
"Ultrasonic Cleaners",
"Annual Prong Check",
"Mohs Scale",
"Prong Setting",
"Diamond Durability"
] |
Color grade | The 4Cs and grading | A color grade rates how close a diamond is to having no color at all, on GIA's D-to-Z scale where D is completely colorless and Z shows a light yellow or brown tint. In this range less color is rarer, and the grade describes the faint body color you're trying not to see. | The standard scale runs from D at the colorless top to Z at the light end, divided into named bands: D to F is colorless, G to J is near colorless, K to M is faint, N to R is very light, and S to Z is light. Graders judge color by comparing a stone, table-down, against a set of masterstones under controlled lighting, s... | [
{
"claim": "GIA's D-to-Z color scale was introduced as part of Richard Liddicoat's International Diamond Grading System in 1953, and the scale starts at D to avoid confusion with earlier trade systems that had used A, B and C.",
"source": "Gemological Institute of America (GIA)",
"date": "1953"
},
{... | [
"the 4Cs",
"clarity grade",
"fluorescence",
"fancy color diamond",
"grading report"
] |
crown | Diamond anatomy | The crown is the upper part of a diamond, the whole section above the girdle. It includes the flat table and the angled facets that ring it. | The crown is everything above the girdle. It holds the flat table at the top and the ring of angled facets around it, which on a round brilliant are the star facets, the bezel (kite) facets, and the upper girdle facets.
The crown has two jobs. It lets light into the stone, and as light leaves, its angled facets bend a... | [] | [
"table",
"girdle",
"pavilion",
"crown angle",
"facet"
] |
Cubic zirconia | Materials and simulants | Cubic zirconia (CZ) is a lab-made crystalline form of zirconium dioxide (ZrO2), stabilized into a cubic structure and cut as an inexpensive, colorless diamond simulant. It is a different material from diamond, softer and denser, and is not a type of diamond. | Zirconium dioxide does not naturally hold a cubic crystal form at room temperature, so cubic zirconia has to be coaxed into one. Makers add a stabilizer such as yttrium oxide or calcium oxide and melt the mixture at extreme temperature (zirconia melts near 2,750 degrees Celsius) using a skull-melting method, in which t... | [
{
"claim": "The skull-melting process for producing cubic zirconia crystals was developed by Soviet researchers at the Lebedev Physical Institute in Moscow, with the method published in 1973.",
"source": "Lebedev Physical Institute (V. V. Osiko group); cubic zirconia history, per encyclopedic and gemologica... | [
"Diamond (the material)",
"Moissanite",
"White sapphire",
"Simulant vs synthetic",
"Mohs hardness"
] |
culet | Diamond anatomy | The culet is the point or small facet at the very bottom of a diamond, where the pavilion facets meet. On many modern stones it is a clean point, graded as none. | The culet is the point or tiny facet at the very bottom of a diamond, where the pavilion facets come together. On many modern stones there's no facet there at all, just a clean point, which a grading report lists as a culet of none or pointed.
Historically, cutters polished a small facet across the bottom tip to guard... | [] | [
"pavilion",
"girdle",
"facet",
"old European cut",
"crown"
] |
cushion cut | Cuts and shapes | A cushion cut is a square-to-rectangular diamond with rounded corners and gently curved sides, faceted in the brilliant style, so that it resembles a pillow. It offers soft, rounded sparkle and a slightly antique character. | The cushion is a modified brilliant whose outline is a square or rectangle with the corners and sides rounded, giving it the pillow shape that names it. Brilliant-style faceting fills the interior, and cushions come in two broad faceting styles: a chunky pattern with larger, bolder facets, and a crushed-ice pattern wit... | [] | [
"elongated cushion",
"old mine cut",
"brilliant cut",
"princess cut",
"crushed-ice faceting",
"length-to-width ratio"
] |
Cut grade | The 4Cs and grading | A cut grade rates how well a diamond's proportions, symmetry, and polish return light to the eye, which is what makes a diamond look bright and lively. GIA grades cut for standard round brilliant diamonds on a five-step scale from Excellent to Poor. | Of the four C's, cut is the one most under human control and the one that most drives how a diamond actually looks. Color and clarity describe the raw crystal; cut describes the craft applied to it. A cutter chooses angles and proportions that either send light back up through the top of the stone or leak it out the bo... | [
{
"claim": "Marcel Tolkowsky's 1919 analysis (Diamond Design) described the proportion relationships underlying the modern round brilliant cut, which has 57 or 58 facets.",
"source": "Marcel Tolkowsky, Diamond Design",
"date": "1919"
},
{
"claim": "GIA released its cut grading system for standar... | [
"the 4Cs",
"round brilliant cut",
"Dutch Marquise",
"carat",
"grading report"
] |
CVD Growth | Lab Grown Diamonds | CVD (Chemical Vapor Deposition) is a method of growing diamond by breaking a carbon-rich gas down inside a vacuum chamber so that carbon atoms settle onto a thin diamond seed and build a crystal up layer by layer. | CVD grows a diamond from gas. The process starts with a thin, flat slice of diamond called a seed, placed inside a sealed vacuum chamber. A carbon-rich gas, usually methane, is fed in along with hydrogen. Energy, typically microwaves, heats the gas into a glowing plasma and breaks the molecules apart, freeing individua... | [] | [
"HPHT Growth",
"Post-Growth Treatment (HPHT Annealing)",
"Lab Grown Diamond",
"Inclusions in Lab Grown Diamonds",
"Diamond Type IIa"
] |
depth percentage | Diamond anatomy | Depth percentage is a diamond's total height (table to culet) divided by its average girdle diameter, expressed as a percentage. It tells you how deep or shallow the stone is cut relative to its width. | Depth percentage is a single number that tells you how tall a diamond is compared with how wide it is. The formula is the total depth, measured from the table on top down to the culet at the bottom, divided by the average girdle diameter, then multiplied by one hundred.
It matters because depth controls how light trav... | [
{
"claim": "Marcel Tolkowsky published influential round brilliant proportions, covering depth and facet angles, in 1919.",
"source": "Marcel Tolkowsky, Diamond Design (1919)",
"date": "1919"
}
] | [
"table percentage",
"girdle",
"pavilion",
"cut",
"crown angle"
] |
Diamond (the material) | Materials and simulants | Diamond is a crystalline form of pure carbon, with each carbon atom bonded to four others in a rigid cubic (isometric) lattice. That structure makes it the hardest known natural material, a 10 on the Mohs scale, and an exceptional conductor of heat. | Diamond is carbon, the same element found in graphite and charcoal, but arranged very differently. In graphite the carbon atoms sit in loose sheets that slide past one another, which is why it feels slippery and marks paper. In diamond every carbon atom is locked to four neighbors in a three-dimensional tetrahedral fra... | [
{
"claim": "The FTC defines a diamond as a mineral consisting essentially of pure carbon crystallized in the isometric system, a definition covering both mined diamonds and Lab Grown Diamonds (the qualifier 'natural' was removed).",
"source": "FTC, Guides for the Jewelry, Precious Metals, and Pewter Industr... | [
"Lab Grown Diamond",
"Mohs hardness",
"Thermal conductivity and diamond testers",
"Toughness vs hardness",
"Moissanite"
] |
Do diamonds come from coal? | History and myths | Mostly no. Almost all natural diamonds form deep in Earth's mantle from carbon-rich material, and most are far older than the land plants that coal is made from, so coal is not their source. | Mostly no. The popular image of a lump of coal squeezed into a diamond makes a nice story, but it does not match the geology. Almost all natural diamonds form deep inside the Earth's mantle, roughly 90 miles or more below the surface, where extreme pressure and heat let carbon crystallize over very long spans of time. ... | [
{
"claim": "Most natural diamonds form deep in Earth's mantle, roughly 150 kilometers (about 90 miles) or more below the surface, under high pressure and temperature, and are carried upward by kimberlite volcanic eruptions.",
"source": "GIA, \"Diamonds from the Deep: How Do Diamonds Form in the Deep Earth?\... | [
"Kimberlite",
"Diamond formation",
"Lab Grown Diamonds",
"HPHT and CVD growth",
"Carbon",
"Mohs scale"
] |
Do Lab Grown Diamonds Cloud or Fade? | Lab Grown Diamonds | No. Lab Grown Diamonds do not cloud, fade, yellow, or degrade over time; a Lab Grown Diamond is crystallized carbon, and its color and clarity are fixed properties of the crystal that don't change with age or wear. | This is one of the most common worries about Lab Grown Diamonds, and the answer is a plain no. A diamond, grown or mined, is carbon locked in an extremely stable crystal structure and rated 10 on the Mohs scale, the hardest of any natural material. Its color and clarity are set by the arrangement of the crystal itself,... | [] | [
"Lab Grown Diamond",
"Diamond Simulant",
"Cubic Zirconia",
"Post-Growth Treatment (HPHT Annealing)",
"Lab-Grown vs Mined Diamonds"
] |
Dutch Marquise | Cuts and shapes | A Dutch Marquise is an elongated hexagonal cut diamond. It has pointed ends and straight, angular sides, and it is a trade name, not an official gemological shape category; on a laboratory report the same shape is described as a Hexagonal Modified Brilliant. | A Dutch Marquise is an elongated hexagon in outline: two pointed ends joined by straight, angular sides, rather than the curved sides of a true marquise. That straight-sided geometry is what separates it from the classic marquise, or navette, which is a boat shape with two points but sides that curve outward. The Dutch... | [
{
"claim": "IGI report LG799689559, issued 2026-05-09 for a diamond cut and sold as a Dutch Marquise, classifies the shape as Hexagonal Modified Brilliant.",
"source": "IGI (International Gemological Institute) diamond grading report No. LG799689559",
"date": "2026-05-09"
}
] | [
"hexagon cut",
"marquise cut",
"navette",
"length-to-width ratio",
"IGI report"
] |
east-west setting | Settings and metals | An east-west setting turns an elongated diamond sideways so its long axis runs across the finger, from side to side, instead of up and down the finger. It is a modern, less common way to set shapes like ovals, marquises, emeralds, and pears. | Most rings set an elongated stone lengthwise, with its long axis running along the finger toward the wrist. An east-west setting rotates that same stone a quarter turn so it lies horizontally, spanning the width of the finger. The stone and the setting are otherwise the same; only the orientation changes. It is a simpl... | [] | [
"solitaire",
"half bezel",
"marquise cut",
"emerald cut",
"Dutch Marquise",
"oval cut"
] |
elongated cushion | Cuts and shapes | An elongated cushion is a cushion cut with a rectangular rather than square outline, stretched so its length clearly exceeds its width while keeping the soft rounded corners and pillow silhouette. It is a longer, more finger-flattering version of the standard cushion. | An elongated cushion is not a separate faceting family; it is a cushion cut, a modified brilliant with rounded corners and curved sides, drawn out to a longer length-to-width ratio. Where a classic cushion is close to square, an elongated cushion typically runs at a ratio of roughly 1.2 to one or more, giving it a rect... | [] | [
"cushion cut",
"oval cut",
"radiant cut",
"length-to-width ratio",
"crushed-ice faceting",
"brilliant cut"
] |
emerald cut | Cuts and shapes | An emerald cut is a rectangular diamond with cut (beveled) corners and step-cut faceting: long, flat, parallel facets stacked in rows like stairs, viewed through a large open table. It trades sparkle for a clean, glassy look and long flashes of light. | The emerald cut is the classic step cut. Instead of the many small triangular facets of a brilliant, it has a smaller number of long rectangular facets running parallel to the girdle, stacked in steps on the crown and pavilion. The corners are cut off at an angle, turning the rectangle into an elongated octagon, and th... | [] | [
"step cut",
"asscher cut",
"radiant cut",
"table",
"four Cs",
"baguette"
] |
Eye-clean | The 4Cs and grading | Eye-clean describes a diamond with no inclusions or blemishes visible to a person with normal vision at a typical viewing distance. It's a practical trade description, not an official grade on the clarity scale. | Clarity grades are assigned under 10x magnification, but you don't wear a diamond at 10x. Eye-clean bridges that gap by describing what the stone looks like to the unaided eye at normal viewing distance, usually taken to be roughly a foot away, in ordinary light. A diamond can carry inclusions that a grader records und... | [] | [
"clarity grade",
"the 4Cs",
"inclusion",
"emerald cut",
"grading report"
] |
facet | Diamond anatomy | A facet is a single flat, polished surface on a diamond. The number, shape, angle, and alignment of all the facets together make up the cut. | A facet is one flat, polished plane on the surface of a diamond. Each one behaves either as a window, letting light pass in or out, or as a mirror, bouncing light around inside the stone. Taken together, the number of facets, their shapes, their angles, and how precisely they line up make up what we call the cut, and t... | [
{
"claim": "Marcel Tolkowsky published an influential set of proportions for the round brilliant cut in 1919.",
"source": "Marcel Tolkowsky, Diamond Design (1919)",
"date": "1919"
},
{
"claim": "Lab Grown Diamonds are real diamonds, the same material as mined diamonds.",
"source": "U.S. FTC ... | [
"table",
"crown",
"pavilion",
"culet",
"cut"
] |
Finding Your Ring Size | Care and buying | Finding your ring size means measuring the finger the ring will sit on to get a size number. The most reliable way is to have a jeweler size you with a set of metal ring gauges, but you can also measure at home with a ring sizer or by measuring a ring that already fits. | Ring size is a standardized measurement of the inside of a band. In the United States it is expressed as a number, with half sizes, that corresponds to a specific inside diameter and circumference. Getting it right matters, because a ring that is too loose can spin or slip off, and one that is too tight is uncomfortabl... | [] | [
"Made-to-Order vs. Ready-to-Ship",
"Ring Resizing",
"Eternity Band",
"Band Width",
"Setting Styles"
] |
Fire (dispersion) | Light and optics | Fire is the flashes of spectral color a diamond throws when white light splits into its component colors inside the stone. Its physical cause is dispersion: a diamond's refractive index is slightly different for each wavelength, so each color bends by a different amount. | White light is a mix of all colors. When it enters a diamond it slows and bends, and because the diamond bends violet light a little more than red light, the colors fan out and leave the stone along slightly different paths. Your eye catches those separated colors as brief red, orange, blue, and violet flashes. That is... | [
{
"claim": "GIA's round brilliant cut grading system (released January 2006) assesses face-up appearance through brightness, fire, and scintillation.",
"source": "GIA (Gemological Institute of America), Diamond Cut grading system, gia.edu / 4cs.gia.edu",
"date": "2006-01"
},
{
"claim": "Under th... | [
"brilliance",
"scintillation",
"refractive index",
"cut grade",
"moissanite"
] |
Fluorescence | The 4Cs and grading | Fluorescence is the visible glow, most often blue, that some diamonds give off under ultraviolet light such as sunlight or a black light. Labs rate its strength from None to Very Strong, and for most diamonds it has little or no effect on how the stone looks in ordinary light. | Roughly speaking, fluorescence happens because certain trace elements and structural features in a diamond absorb ultraviolet energy and re-emit it as visible light. The common color is blue, though other colors occur. GIA reports fluorescence on a scale of None, Faint, Medium, Strong, and Very Strong, describing the r... | [
{
"claim": "A GIA study published in Gems & Gemology (Winter 1997) found that, for the average observer, blue fluorescence had no systematic effect on diamond appearance, and strongly blue fluorescent diamonds were perceived slightly better in the face-up position.",
"source": "GIA, Gems & Gemology (Moses e... | [
"color grade",
"the 4Cs",
"grading report",
"certification labs",
"clarity grade"
] |
FTC Definition of Diamond (2018) | Lab Grown Diamonds | In 2018 the U.S. Federal Trade Commission revised its Jewelry Guides and removed the word "natural" from the definition of a diamond, formally recognizing that a diamond grown in a laboratory is still a diamond. | The Federal Trade Commission's Jewelry Guides are the rules that govern how diamonds and jewelry can be described and marketed in the United States. For decades the guides defined a diamond, in effect, as a natural mineral made of carbon crystallized in the isometric system. The word "natural" carried an important impl... | [
{
"claim": "The FTC revised its Jewelry Guides and removed the word 'natural' from the definition of a diamond.",
"source": "FTC Jewelry Guides (revised)",
"date": "2018"
},
{
"claim": "The FTC advised sellers to disclose lab-grown origin and accepted qualifiers such as 'laboratory-grown', 'labo... | [
"Lab Grown Diamond",
"Lab-Grown vs Mined Diamonds",
"Grading Report",
"Diamond Simulant",
"GIA vs IGI Grading"
] |
girdle | Diamond anatomy | The girdle is the narrow band around the widest part of a diamond, where the crown meets the pavilion. It forms the stone's outline and is where a setting grips it. | The girdle is the dividing line of a diamond. Everything above it is the crown; everything below is the pavilion. Its outline is the shape you name the stone by, round, oval, cushion, and so on, and it is the practical place a jeweler grips the stone, whether with prongs or a surrounding bezel.
Girdle thickness is gra... | [] | [
"crown",
"pavilion",
"culet",
"depth percentage",
"facet"
] |
Grading report | The 4Cs and grading | A grading report is a document from an independent gemological laboratory that describes a diamond's measured characteristics, including the 4Cs, on a standard form. It's a scientific description of the stone, not a statement of monetary value or an appraisal. | A typical report lists the shape and cutting style, the measurements in millimeters, the carat weight, the color and clarity grades, and, for round brilliants, a cut grade, along with polish, symmetry, fluorescence, and any laser inscription. Many reports include a plotting diagram that maps the stone's clarity charact... | [
{
"claim": "IGI issues full 4C grading reports for Lab Grown Diamonds.",
"source": "International Gemological Institute (IGI)",
"date": "2026"
},
{
"claim": "GIA moved its Lab Grown Diamond reports to a Premium and Standard tier structure on October 1, 2025.",
"source": "Gemological Institut... | [
"the 4Cs",
"certification labs",
"laser inscription",
"clarity grade",
"appraisal"
] |
half bezel | Settings and metals | A half bezel, also called a semi-bezel or open bezel, wraps metal around only two sides of the diamond, usually the left and right, leaving the other two sides open. It shields the stone's long sides while letting in more light than a full bezel. | A half bezel is the middle ground between a full bezel and prongs. Two curved walls of metal cup the sides of the stone and hold it firmly, while the top and bottom, or the two ends of an elongated stone, stay open. That open space lets light enter from more directions, so a half-bezeled diamond usually looks brighter ... | [] | [
"bezel setting",
"prong setting",
"V-tip prong",
"east-west setting",
"girdle",
"solitaire"
] |
halo | Settings and metals | A halo is a ring of small diamonds set around a larger center stone, framing it with a circle of sparkle that makes the center look bigger and brighter. It is one of the most popular center-stone settings. | A halo surrounds the center diamond with a continuous border of small accent stones, usually pave-set, so the frame reads as one bright ring of light. The main reason people choose a halo is size and sparkle for the money: the border adds visual weight, so a center stone can look noticeably larger than its carat weight... | [] | [
"hidden halo",
"pave",
"solitaire",
"cathedral setting",
"carat",
"oval cut"
] |
Hearts and arrows | Light and optics | Hearts and arrows is a pattern of eight symmetrical arrows seen face-up and eight hearts seen from the back, visible in a round brilliant cut with very precise optical symmetry and viewed through a special scope. It is a sign of exacting cut symmetry, not a grade of its own. | The pattern comes from the way a round brilliant's facets reflect one another. When the eight pavilion main facets and the eight crown facets are cut to matching angles and spaced evenly, their reflections line up into eight arrowheads when you look straight down through the table, and into eight heart shapes when you ... | [
{
"claim": "The hearts and arrows pattern was first observed in Japan during the 1980s, seen in round brilliants of exceptional symmetry through a special viewer, and spread to the United States and Europe over the following decade.",
"source": "IGI (International Gemological Institute), education, igi.org"... | [
"scintillation",
"light performance",
"cut grade",
"optical symmetry",
"round brilliant"
] |
hexagon cut | Cuts and shapes | A hexagon cut is a diamond with a six-sided outline. It is a geometric fancy shape that can be faceted with long parallel facets, in the brilliant style, or as a mix of the two, and can be cut as a regular hexagon or elongated. | A hexagon cut is defined by its outline: six straight sides meeting at six corners. Beyond that, it is an open category. A hexagon can be faceted with long, flat facets stacked parallel to the girdle for a clean, geometric look, or in the brilliant style for more sparkle, or a blend of the two, so two stones both calle... | [] | [
"Dutch Marquise",
"emerald cut",
"step cut",
"bezel setting",
"marquise cut",
"brilliant cut"
] |
hidden halo | Settings and metals | A hidden halo is a ring of tiny diamonds set on the underside of the center stone's setting, circling the base where it meets the band, so the extra sparkle shows only from the side and profile, not when you look straight down at the ring. | A hidden halo puts a halo where you do not expect one. Instead of framing the center diamond on top, the small stones ring the outside of the basket or collar that holds the center stone, sitting just below it. From directly above, the center diamond looks like a clean solitaire with no frame. Turn the ring to the side... | [] | [
"halo",
"pave",
"solitaire",
"cathedral setting",
"prong setting",
"girdle"
] |
HPHT Growth | Lab Grown Diamonds | HPHT (High Pressure High Temperature) is a method of growing diamond by dissolving carbon in molten metal and letting it crystallize onto a diamond seed under intense pressure and heat, recreating the kind of conditions under which diamonds form deep in the earth. | HPHT recreates, inside a machine, the pressure and heat that form diamonds underground. A large press squeezes a sealed growth cell to enormous pressure while heating it to a high temperature. Inside sits a carbon source, usually graphite, along with a molten metal that acts as a solvent, commonly iron, nickel, or coba... | [] | [
"CVD Growth",
"Post-Growth Treatment (HPHT Annealing)",
"Lab Grown Diamond",
"Inclusions in Lab Grown Diamonds",
"Lab-Grown vs Mined Diamonds"
] |
Inclusions in Lab Grown Diamonds | Lab Grown Diamonds | Inclusions in a Lab Grown Diamond are the tiny internal features, such as metallic flecks, dark crystals, or faint growth lines, that form while the diamond grows. They're the Lab Grown Diamond counterpart to the inclusions in mined diamonds, and they're what graders read to judge clarity and to confirm how a stone was... | Every diamond has an interior, and most have small features inside called inclusions. Lab Grown Diamonds are no exception. What differs is the kind of inclusion, because it reflects how the stone was grown.
HPHT diamonds grow inside a molten metal, so they can carry tiny metallic flux inclusions, specks of the iron, n... | [
{
"claim": "IGI issues full 4C grading reports for Lab Grown Diamonds, including clarity.",
"source": "IGI",
"date": "2026"
},
{
"claim": "GIA places Lab Grown Diamonds in descriptive Premium and Standard tiers rather than issuing individual 4C grades.",
"source": "GIA",
"date": "2025-10... | [
"HPHT Growth",
"CVD Growth",
"Lab Grown Diamond",
"Diamond Clarity",
"The 4Cs",
"Grading Report"
] |
Insuring an Engagement Ring | Care and buying | Insuring an engagement ring means buying coverage that pays to repair or replace it if it is lost, stolen, or damaged, either as an add-on to a home or renters policy or as a standalone jewelry policy. You will usually need documentation such as the grading report, the receipt, and an appraisal. | An engagement ring is worn constantly and can be lost, stolen, or damaged, and standard home or renters insurance often limits what it will pay for jewelry. Insurance closes that gap. There are two common routes. The first is a rider, also called a floater or scheduled personal property, added to an existing homeowners... | [] | [
"Appraisal",
"Grading Report",
"Verifying a Grading Report",
"Annual Prong Check",
"Replacement Value"
] |
Lab Grown Diamond | Lab Grown Diamonds | A Lab Grown Diamond is a real diamond, pure crystallized carbon with the same crystal structure, hardness, and optical properties as a mined diamond, produced in a laboratory instead of forming underground. The only difference is where the carbon crystallized. | A Lab Grown Diamond is not an imitation or a stand-in. It's the same material as a mined diamond: carbon atoms locked into the same cubic crystal lattice, with the same hardness (10 on the Mohs scale), the same brilliance, and the same fire. Set a grown and a mined diamond of matching grades side by side and no one, in... | [
{
"claim": "The FTC removed the word 'natural' from its definition of a diamond, recognizing that a Lab Grown Diamond is a diamond.",
"source": "FTC Jewelry Guides (revised)",
"date": "2018"
},
{
"claim": "GIA moved Lab Grown Diamonds to descriptive Premium and Standard tiers instead of individu... | [
"CVD Growth",
"HPHT Growth",
"FTC Definition of Diamond (2018)",
"Lab-Grown vs Mined Diamonds",
"The 4Cs",
"Diamond Simulant"
] |
Lab-Grown vs Mined Diamonds | Lab Grown Diamonds | A Lab Grown Diamond and a mined diamond are the same material, with the same hardness, brilliance, and fire; they differ in origin (a laboratory versus the earth) and usually in price, not in what they are. | Start with what's identical, because most of it is. A Lab Grown Diamond and a mined diamond are both pure carbon in the same crystal structure. Both are a 10 on the Mohs scale, the hardest of any natural material. Both bend and return light the same way, so they show the same brilliance and fire. Both are graded by the... | [
{
"claim": "Lab-grown and mined diamonds are both recognized as diamonds under the FTC's revised definition.",
"source": "FTC Jewelry Guides (revised)",
"date": "2018"
},
{
"claim": "IGI issues full 4C grading reports for Lab Grown Diamonds.",
"source": "IGI",
"date": "2026"
},
{
... | [
"Lab Grown Diamond",
"FTC Definition of Diamond (2018)",
"Do Lab Grown Diamonds Cloud or Fade?",
"The 4Cs",
"Diamond Simulant",
"Grading Report"
] |
Laser inscription | The 4Cs and grading | A laser inscription is text, usually a report number, micro-engraved onto a diamond's girdle with a fine laser and readable under magnification. It lets you match a specific stone to its grading report, and on Lab Grown Diamonds it commonly marks the stone as laboratory-grown. | The girdle is the thin outer edge where the top and bottom of a diamond meet, and it's the standard place for an inscription because it doesn't interfere with how light moves through the stone. The characters are tiny, invisible to the naked eye, and read with a loupe or microscope. Most often the inscription is the gr... | [
{
"claim": "GIA laser-inscribes \"Laboratory-Grown\" and the report number on the girdle of Lab Grown Diamonds.",
"source": "Gemological Institute of America (GIA)",
"date": "2026"
},
{
"claim": "IGI historically inscribed \"LAB GROWN\" on laboratory-grown diamonds and, from early February 2023,... | [
"grading report",
"certification labs",
"girdle",
"the 4Cs"
] |
length-to-width ratio | Diamond anatomy | Length-to-width ratio is a diamond's length divided by its width, both measured across the girdle. It describes how square or elongated the outline is. | Length-to-width ratio comes straight from a diamond's outline measurements: the length in millimeters divided by the width in millimeters, both taken across the girdle. A ratio near 1.00 is square or round; the higher the number, the more elongated the stone.
It is used mainly for fancy (non-round) shapes to describe ... | [
{
"claim": "The Dutch Marquise is an elongated hexagonal cut (a trade name; an IGI report describes it as 'Hexagonal Modified Brilliant') with a length-to-width ratio of roughly 1.5 to 2.0.",
"source": "Stienhardt & Stones Dutch Marquise reference; IGI diamond report",
"date": "2026-07-10"
}
] | [
"bow-tie effect",
"Dutch Marquise",
"oval cut",
"marquise cut",
"girdle"
] |
Light performance | Light and optics | Light performance is an umbrella term for how well a diamond takes in light and returns it to the eye, combining brightness, fire, scintillation, and the absence of light leakage. It is assessed with ray tracing and with viewers like the ASET and the Idealscope rather than by a single universal grade. | Light performance is the practical question behind cut: of all the light that reaches a diamond, how much comes back to your eye as brightness, colored fire, and sparkle, and how much is wasted by leaking out the bottom. A stone with strong light performance returns most of the light it gathers and spreads it evenly ac... | [
{
"claim": "GIA's round brilliant cut grading system (released January 2006) assigns a cut grade from Excellent to Poor based on proportions and on brightness, fire, and scintillation.",
"source": "GIA (Gemological Institute of America), Diamond Cut grading system, gia.edu / 4cs.gia.edu",
"date": "2006-... | [
"brilliance",
"fire (dispersion)",
"scintillation",
"windowing and light leakage",
"cut grade"
] |
Made-to-Order vs. Ready-to-Ship | Care and buying | Made-to-order means your ring is built and set after you place the order, so you can choose the stone, setting, metal, and size, but it takes longer. Ready-to-ship means the ring is already finished and in stock, so it arrives fast with less to customize. | These are two ways a finished ring reaches you, and the difference is mostly time versus choice.
A made-to-order ring, sometimes called built-to-order, is assembled after you buy it. You typically select the center stone, the setting style, the metal, and the finger size, and the piece is set and finished to those spe... | [] | [
"Finding Your Ring Size",
"The Eye-Clean Buying Strategy",
"Setting Styles",
"Ring Resizing",
"Grading Report"
] |
marquise cut (navette) | Cuts and shapes | A marquise cut, also called a navette, is an elongated, boat-shaped diamond with two pointed ends and gently curved sides, faceted in the brilliant style. It shows one of the largest face-up spreads per carat of any shape. | The marquise is a modified brilliant with an elongated outline that comes to a point at each end. The sides curve outward from the middle, and brilliant-style facets fill the interior, so it sparkles like a round or an oval rather than flashing like a step cut. It is also called a navette, from the French for a small b... | [
{
"claim": "Diamond is the maximum, a 10, on the Mohs scale of mineral hardness.",
"source": "Mohs scale of mineral hardness",
"date": "1812"
}
] | [
"navette",
"brilliant cut",
"pear cut",
"bow-tie effect",
"prong setting",
"Dutch Marquise"
] |
Mohs hardness | Materials and simulants | The Mohs scale is a 1-to-10 ordinal ranking of a mineral's resistance to being scratched, where a higher-numbered mineral can scratch any lower-numbered one. Diamond sits at 10, the top of the scale. | The Mohs scale was devised in 1812 by the German mineralogist Friedrich Mohs as a simple field test. Take two minerals, try to scratch one with the other, and whichever leaves a mark is the harder. Mohs fixed ten reference minerals as benchmarks, from talc at 1 (soft enough to mark with a fingernail) up through gypsum,... | [
{
"claim": "The Mohs hardness scale (an ordinal 1-to-10 scratch scale running talc 1, gypsum 2, calcite 3, fluorite 4, apatite 5, feldspar 6, quartz 7, topaz 8, corundum 9, diamond 10) was devised by the German mineralogist Friedrich Mohs.",
"source": "Friedrich Mohs, Versuch einer Elementar-Methode zur nat... | [
"Toughness vs hardness",
"Diamond (the material)",
"Moissanite",
"White sapphire",
"Cubic zirconia"
] |
Moissanite | Materials and simulants | Moissanite is silicon carbide (SiC), a hard, brilliant crystalline material used both as a diamond simulant and as a gemstone in its own right. Almost all moissanite in jewelry is lab-created, because the natural mineral is vanishingly rare. | Moissanite is not a type of diamond, and it is not a lower grade of anything. It is a separate material, silicon carbide, with its own chemistry and its own look. The French chemist Henri Moissan found small crystals in fragments of a meteorite from Canyon Diablo in Arizona in 1893, and first mistook them for diamond. ... | [
{
"claim": "Henri Moissan found small crystals in fragments of a meteorite from Canyon Diablo, Arizona, and initially believed them to be diamond.",
"source": "Historical account of Moissan's meteorite analysis, per mineralogical references (Mindat.org, entry for moissanite)",
"date": "1893"
},
{
... | [
"Diamond (the material)",
"Simulant vs synthetic",
"Cubic zirconia",
"Thermal conductivity and diamond testers",
"Mohs hardness"
] |
moval | Cuts and shapes | A moval is a hybrid diamond shape between a marquise and an oval: an elongated brilliant cut with the soft curved sides of an oval and gently pointed, or slightly tapered, ends. Its name is a blend of the words marquise and oval. | The moval sits on the spectrum between two familiar shapes. An oval has fully rounded ends; a marquise has two sharp points. A moval is in between: an elongated modified brilliant with curved sides like an oval, but ends that come to a gentle, softened point rather than a full curve or a sharp tip. The name is simply a... | [] | [
"oval cut",
"marquise cut",
"brilliant cut",
"bow-tie effect",
"length-to-width ratio",
"pear cut"
] |
old european cut | Cuts and shapes | An old European cut is an antique round brilliant: a circular, hand-cut diamond with a high crown, a small table, a deep pavilion, and a large flat culet. It is the direct ancestor of the modern round brilliant. | The old European cut is the round member of the antique brilliant family and the closest predecessor to today's round brilliant. Like the modern round it has a circular outline and roughly the same count of brilliant-style facets, but its proportions come from the hand-cutting era: a tall crown, a small table, a steep ... | [] | [
"old mine cut",
"round brilliant cut",
"culet",
"brilliant cut",
"crown",
"table"
] |
old mine cut | Cuts and shapes | An old mine cut is an antique brilliant cut with a squarish, cushion-like outline, a high crown, a small table, a deep pavilion, and a large flat culet at the bottom. It is an early, hand-cut ancestor of the modern cushion and round brilliants. | The old mine cut is a brilliant-family cut from the era of hand cutting, before modern proportions were standardized. Its outline is roughly square with rounded corners, close to a cushion, and its proportions are distinctive: a tall crown, a small table up top, a deep pavilion, and a large culet, the facet polished fl... | [] | [
"old european cut",
"cushion cut",
"culet",
"brilliant cut",
"crown",
"table"
] |
oval cut | Cuts and shapes | An oval cut is an elongated, rounded diamond with brilliant-style faceting, essentially a round brilliant stretched along one axis. It keeps much of a round's sparkle while covering more of the finger. | The oval is a modified brilliant: it uses the same family of triangular and kite-shaped facets as a round brilliant, arranged around an elongated closed curve with no points or corners. Length-to-width ratio is a matter of taste, but most ovals are cut somewhere around 1.3 to 1.5 to one.
Face-up, an oval reads larger ... | [] | [
"round brilliant cut",
"brilliant cut",
"bow-tie effect",
"moval",
"length-to-width ratio",
"marquise cut"
] |
pave | Settings and metals | Pave (pronounced pah-vay, from the French for paved) is a technique that packs many tiny diamonds close together, held by minute metal beads, so the surface reads as continuous sparkle rather than individual stones. Micro-pave uses especially small stones. | In pave, a setter drills seats for a row or field of small diamonds and raises tiny beads of metal from the surrounding surface to hold each stone at its corners. Because the stones sit close and the beads are minute, the eye sees a paved sheet of light rather than separate settings, which is where the name comes from.... | [] | [
"halo",
"hidden halo",
"channel setting",
"solitaire",
"girdle",
"carat"
] |
pavilion | Diamond anatomy | The pavilion is the lower part of a diamond, the cone-shaped section below the girdle that tapers toward the culet. Its angled facets reflect light back up toward your eye. | The pavilion is where a diamond gets most of its brightness. Its angled facets act as internal mirrors: light that comes in through the table and crown strikes the pavilion walls and is reflected back up and out toward your eye. When the pavilion angle is close to ideal, most of that light returns through the top and t... | [] | [
"crown",
"girdle",
"culet",
"pavilion angle",
"depth percentage"
] |
pear cut | Cuts and shapes | A pear cut is a teardrop-shaped diamond with one softly rounded end and one point, faceted in the brilliant style. It reads as half oval and half marquise, and is also called a teardrop cut. | The pear is a modified brilliant: brilliant-style triangular and kite facets fill a closed outline that is round at one end and tapers to a single point at the other. In effect it is half oval and half marquise, and it is conventionally worn with the point facing up the hand, toward the fingernail.
Face-up, the pear e... | [] | [
"marquise cut",
"oval cut",
"brilliant cut",
"bow-tie effect",
"prong setting",
"length-to-width ratio"
] |
platinum | Settings and metals | Platinum is a naturally white, dense, and durable precious metal used for fine jewelry, typically alloyed to about 90 to 95 percent purity. Unlike white gold, its white color is natural and permanent, so it never needs rhodium plating. | Platinum is a premium setting metal prized for three things: color, density, and security. Its color is a true, cool white that comes from the metal itself, not from a coating, so a platinum ring stays white for life with no replating. Jewelry platinum is usually marked 950 or 900, meaning 95 or 90 percent pure platinu... | [] | [
"white gold and rhodium plating",
"yellow gold",
"prong setting",
"bezel setting",
"ring sizing and resizing",
"solitaire"
] |
portuguese cut | Cuts and shapes | A Portuguese cut is a highly faceted round cut with multiple rows of triangular facets stacked above and below the girdle, giving it far more facets than a standard round brilliant and an intense, lattice-like sparkle. It is a specialty cut, more common in colored gemstones but used for diamonds as well. | The Portuguese cut is defined by its dense, layered faceting. Where a standard round brilliant has a single main row of facets on the crown and pavilion, a Portuguese cut adds extra rows of triangular and rhombus-shaped facets, typically two or more tiers on each half of the stone. The result is a much higher facet cou... | [] | [
"round brilliant cut",
"brilliant cut",
"scintillation",
"facet",
"girdle",
"old european cut"
] |
Post-Growth Treatment (HPHT Annealing) | Lab Grown Diamonds | Post-growth treatment is a process applied to a Lab Grown Diamond after it's grown to improve its color, most often HPHT annealing, in which the finished crystal is exposed to high pressure and high temperature that shift its color toward colorless. The change is permanent and is disclosed on the grading report. | Some Lab Grown Diamonds, particularly those made by CVD, come out of growth with a faint brown or gray cast. The color comes from the way atoms and tiny gaps are arranged in the crystal as it forms. Post-growth treatment corrects this. The most common form is HPHT annealing: the finished diamond is placed under high pr... | [] | [
"CVD Growth",
"HPHT Growth",
"Lab Grown Diamond",
"Grading Report",
"Diamond Color"
] |
princess cut | Cuts and shapes | A princess cut is a square diamond with sharp, uncut corners and brilliant-style faceting, technically a square modified brilliant. It offers a lot of sparkle in a clean, contemporary square outline. | The princess is a modified brilliant with a square, sometimes slightly rectangular, outline. Unlike the emerald, Asscher, and radiant, its four corners are left sharp and pointed rather than cut off. Inside, it uses brilliant-style faceting, with chevron-shaped facets on the pavilion that create bright, fiery sparkle a... | [
{
"claim": "Diamond is a 10, the maximum, on the Mohs scale of mineral hardness.",
"source": "Mohs scale of mineral hardness",
"date": "1812"
}
] | [
"brilliant cut",
"radiant cut",
"cushion cut",
"Mohs hardness",
"prong setting",
"four Cs"
] |
prong setting | Settings and metals | A prong setting holds a diamond with several thin metal claws that grip the stone near its girdle and lift it up so light can reach it from all sides. It is the most common way to set a center stone. | A prong setting, also called a claw setting, uses three or more slender metal fingers that rise from the base of the setting and bend over the edge of the stone to lock it in place. The most common counts are four prongs and six prongs. Four prongs show more of the diamond and let in more light, while six prongs hold t... | [] | [
"bezel setting",
"V-tip prong",
"solitaire",
"cathedral setting",
"girdle",
"halo"
] |
radiant cut | Cuts and shapes | A radiant cut is a rectangular or square diamond with cut corners and brilliant-style faceting. It combines the trimmed corners of an emerald cut with the sparkling, triangular-facet interior of a round, which makes it a mixed cut. | The radiant is the bridge between the two main faceting families. Its outline looks like an emerald cut, a rectangle or square with the corners cropped off, but its interior is faceted in the brilliant style, with many small triangular and kite facets instead of long step-cut rows. That combination is why it is called ... | [] | [
"emerald cut",
"princess cut",
"cushion cut",
"brilliant cut",
"mixed cut",
"length-to-width ratio"
] |
Refractive index | Light and optics | Refractive index (n) is a number that says how much a material slows and bends light compared with a vacuum. Diamond's is about 2.417, among the highest of any common transparent material, and it is the root cause of a diamond's brightness. | Light travels fastest in a vacuum. In any transparent material it slows down, and the ratio of the vacuum speed to the speed inside the material is the refractive index, written n. A higher n means light slows more and bends more sharply when it crosses the surface at an angle. For diamond, n is about 2.417 (measured w... | [
{
"claim": "Under the U.S. FTC Jewelry Guides, a Lab Grown Diamond is a real diamond, chemically and physically identical to a mined diamond, so its refractive index is the same.",
"source": "U.S. Federal Trade Commission, revised Jewelry Guides",
"date": "2018"
}
] | [
"total internal reflection",
"brilliance",
"fire (dispersion)",
"critical angle",
"moissanite"
] |
ring sizing and resizing | Settings and metals | Ring sizing is measuring the finger to find the right band size, and resizing is a jeweler's later adjustment of an existing ring up or down to fit. Most plain metal bands resize easily, while rings with stones all the way around, or certain designs, may resize little or not at all. | Ring size is expressed on a numbered scale, in the United States as whole and half sizes with quarter sizes available, that corresponds to the inside circumference of the band. Fingers change through the day and the year: they swell in heat and shrink in cold, so the best measurement is taken when your hands are at a n... | [] | [
"yellow gold",
"white gold and rhodium plating",
"platinum",
"bezel setting",
"pave",
"solitaire"
] |
round brilliant cut | Cuts and shapes | A round brilliant cut is a circular diamond with 57 or 58 facets arranged in the brilliant style, triangular and kite-shaped facets radiating from the center, to maximize light return. It is the most common diamond cut and the benchmark against which other shapes are compared. | The round brilliant belongs to the brilliant faceting family, meaning its facets are triangular and kite-shaped and fan out from the center rather than running in straight parallel rows. A standard round brilliant has 57 facets, or 58 if a small facet called a culet is polished onto the point at the bottom. The modern ... | [
{
"claim": "The modern round brilliant's light-optimizing proportions were set out by Marcel Tolkowsky in Diamond Design.",
"source": "Marcel Tolkowsky, Diamond Design",
"date": "1919"
},
{
"claim": "A Lab Grown Diamond is a real diamond.",
"source": "FTC Jewelry Guides",
"date": "2018"
... | [
"brilliant cut",
"oval cut",
"old european cut",
"facet",
"culet",
"Lab Grown Diamond"
] |
Scintillation | Light and optics | Scintillation is a diamond's sparkle: the play of light and dark flashes seen as the stone, the light, or the viewer moves. In GIA's cut model it covers both the flashes of light and the pattern of light and dark areas across the stone. | Brilliance and fire describe light returning at a single instant. Scintillation is about change over time. As a diamond tips and turns, each facet switches between catching a light source and falling into shadow, so the stone flickers with quick flashes. Those flashes are the sparkle. The second half of scintillation i... | [
{
"claim": "GIA's round brilliant cut grading system (released January 2006) treats scintillation as one of three face-up appearance components, alongside brightness and fire, in a cut grade from Excellent to Poor.",
"source": "GIA (Gemological Institute of America), Diamond Cut grading system, gia.edu / 4c... | [
"brilliance",
"fire (dispersion)",
"hearts and arrows",
"light performance",
"cut grade"
] |
Simulant vs synthetic (the distinction) | Materials and simulants | A synthetic diamond (a Lab Grown Diamond) is the same material as a mined diamond, grown in a lab instead of forming in the Earth. A simulant is a different material that merely looks like diamond. In short: a Lab Grown Diamond is a real diamond, a simulant is not. | This is the single most useful distinction in the whole subject, and it is often blurred. Synthetic and simulant are not synonyms.
A synthetic diamond, better called a Lab Grown Diamond, has the identical chemistry (pure carbon), crystal structure, hardness, and optical properties of a mined diamond. It is grown by hi... | [
{
"claim": "The FTC's revised Jewelry Guides define a diamond by composition and require Lab Grown Diamonds to be clearly disclosed as such, while simulants (imitations) must be disclosed as not being diamonds.",
"source": "FTC, Guides for the Jewelry, Precious Metals, and Pewter Industries (Federal Registe... | [
"Lab Grown Diamond",
"Diamond (the material)",
"Moissanite",
"Cubic zirconia",
"White sapphire"
] |
solitaire | Settings and metals | A solitaire is a ring set with a single diamond and no accent stones. The name refers to that one solitary stone, and it is the classic, most recognizable engagement ring style. | A solitaire puts all the attention on one diamond. The setting, most often a prong setting but sometimes a bezel, holds the single stone on a plain metal band with no side stones, halo, or pave. Because nothing competes with it, the center stone's cut, shape, and proportions carry the whole look, so a solitaire rewards... | [
{
"claim": "Lab Grown Diamonds have essentially the same optical, physical, and chemical properties as mined diamonds and are properly called diamonds; the U.S. Federal Trade Commission recognized this in its revised Jewelry Guides.",
"source": "U.S. Federal Trade Commission, Guides for the Jewelry, Preciou... | [
"prong setting",
"bezel setting",
"halo",
"cathedral setting",
"round brilliant",
"Dutch Marquise"
] |
table | Diamond anatomy | The table is the large, flat facet on the top of a diamond. It is the single biggest facet on the stone and sits at the center of the crown. | The table is the main window into a diamond. Most light enters and exits through it, so it does a lot of the work of showing brightness. On a round brilliant the table is an eight-sided facet at the very center of the top; on step cuts like the emerald cut it is a rectangle.
Its size relative to the width of the stone... | [] | [
"crown",
"table percentage",
"facet",
"girdle",
"brilliance"
] |
table percentage | Diamond anatomy | Table percentage is the width of a diamond's table facet divided by its average girdle diameter, expressed as a percentage. It describes how large the top window is relative to the whole stone. | Table percentage describes how big a diamond's top window is relative to the whole stone. The formula is the width of the table facet divided by the average girdle diameter, multiplied by one hundred. On a round brilliant the table width is measured straight across the eight-sided table.
The number captures a balance.... | [
{
"claim": "Marcel Tolkowsky's 1919 proportions for the round brilliant specified a table size.",
"source": "Marcel Tolkowsky, Diamond Design (1919)",
"date": "1919"
}
] | [
"table",
"depth percentage",
"crown",
"facet",
"cut"
] |
The 4Cs | The 4Cs and grading | The 4Cs are the four standard measures of a polished diamond's quality: carat weight, color, clarity, and cut. They're the shared vocabulary the whole diamond trade uses to describe and compare stones, popularized and standardized by GIA over the twentieth century. | Each C answers a different question. Carat is how much the diamond weighs. Color is how little body color it has, from colorless down to a light tint. Clarity is how free it is of inclusions and blemishes under magnification. Cut is how well its proportions and finish return light. Read together, the four give a compac... | [
{
"claim": "The Gemological Institute of America (GIA), a nonprofit, was founded by Robert M. Shipley in 1931.",
"source": "Gemological Institute of America (GIA)",
"date": "1931"
},
{
"claim": "GIA's Robert Shipley popularized the \"four Cs\" mnemonic in the 1940s as a teaching device.",
"s... | [
"carat",
"color grade",
"clarity grade",
"cut grade",
"grading report",
"certification labs"
] |
The Cullinan diamond | History and myths | The Cullinan is the largest gem-quality rough diamond ever found, at 3,106 carats. Discovered in South Africa in 1905, it was cut into stones that include the two largest diamonds in the British Crown Jewels. | The Cullinan is the largest gem-quality rough diamond ever discovered, weighing 3,106 carats before cutting. It was found in 1905 at the Premier mine near Pretoria, in what is now South Africa, and was named after Thomas Cullinan, the chairman of the mining company. In 1907 the government of the Transvaal bought the st... | [
{
"claim": "The Cullinan, at 3,106 carats, is the largest gem-quality rough diamond ever found; it was discovered in 1905 at the Premier mine near Pretoria, South Africa.",
"source": "Task anchor (3,106 carats, found 1905); Encyclopaedia Britannica",
"date": "1905"
},
{
"claim": "The diamond was... | [
"The Hope Diamond",
"Carat",
"Diamond cutting",
"Rough diamond",
"Round brilliant cut"
] |
The Eye-Clean Buying Strategy (Prioritize Cut) | Care and buying | The eye-clean strategy is a way to get the most beautiful diamond for your budget: put your money into cut, then pick a clarity grade that looks flawless to the naked eye rather than paying for perfection under magnification. Eye-clean means no inclusions are visible without magnification at a normal viewing distance. | Of the 4Cs, cut has the biggest effect on how a diamond actually looks. Cut is how well the stone's facets are proportioned and finished, and it governs how much light comes back to your eye as brightness, fire, and sparkle. A poorly cut diamond looks dull no matter how good its other grades are, while an excellently c... | [
{
"claim": "The modern round brilliant has 57 or 58 facets, and its light-returning proportions trace to Marcel Tolkowsky's published analysis in Diamond Design.",
"source": "Marcel Tolkowsky, Diamond Design",
"date": "1919"
},
{
"claim": "Lab Grown Diamonds are real diamonds graded on the same ... | [
"The 4Cs",
"Cut",
"Clarity",
"Eye-Clean",
"Inclusions",
"Round Brilliant"
] |
The Hope Diamond | History and myths | The Hope Diamond is a 45.52-carat deep grayish-blue diamond, colored by trace boron, on public display at the Smithsonian's National Museum of Natural History in Washington. | The Hope Diamond is a 45.52 carat deep grayish-blue diamond, described by the Smithsonian as the largest known deep-blue diamond. It has been on public display at the Smithsonian's National Museum of Natural History in Washington since the jeweler Harry Winston donated it in 1958. Winston famously sent it to the museum... | [
{
"claim": "The Hope Diamond weighs 45.52 carats, is a deep grayish-blue color described by the Smithsonian as the largest known deep-blue diamond, and is displayed at the Smithsonian's National Museum of Natural History.",
"source": "Smithsonian National Museum of Natural History",
"date": "2026"
},
... | [
"The Cullinan diamond",
"Fancy color diamonds",
"Blue diamonds (Type IIb, boron)",
"Fluorescence and phosphorescence",
"Carat"
] |
The months-of-salary rule | History and myths | The idea that an engagement ring should cost a set share of your income (one, two, or three months' salary) is not an old tradition or etiquette rule. It comes from De Beers advertising, and you are free to spend whatever fits your budget. | There is no traditional rule that a ring must cost one, two, or three months of your income. The guideline comes from De Beers advertising, produced by the agency N.W. Ayer from the late 1930s onward, and it was written to give shoppers a number to aim for. The specific figure shifted over time: a one month benchmark a... | [
{
"claim": "The guideline to spend a fixed share of salary on an engagement ring originated in De Beers advertising created by N.W. Ayer, from the late 1930s onward, rather than in older tradition or etiquette.",
"source": "Task anchor (months-of-salary guideline, De Beers / N.W. Ayer advertising, 1930s onw... | [
"A Diamond Is Forever",
"The 4Cs",
"Cut grade",
"Engagement ring history",
"Lab Grown Diamonds"
] |
The three-stone ring | History and myths | A three-stone ring sets a center diamond between two side stones. Its popular "past, present, future" meaning comes from a De Beers campaign around the year 2000, developed by the advertising agency J. Walter Thompson. | A three-stone ring is what it sounds like: a center diamond flanked by two side stones, usually set in a symmetrical row. It is a classic, versatile look, and the side stones can echo the center shape or contrast with it.
The familiar meaning attached to it, that the three diamonds stand for the past, present, and fut... | [
{
"claim": "The \"past, present, future\" meaning of the three-stone diamond ring comes from a De Beers marketing campaign developed by the agency J. Walter Thompson around the year 2000, which promoted the three-stone ring as an anniversary and milestone piece.",
"source": "Jewelry and advertising trade re... | [
"A Diamond Is Forever",
"Engagement ring history",
"Solitaire setting",
"Side stones",
"The 4Cs"
] |
Thermal conductivity and diamond testers | Materials and simulants | A diamond tester is a handheld probe that measures how fast a stone carries heat away, exploiting the fact that diamond conducts heat better than almost any other material. Because a Lab Grown Diamond is diamond, it reads as diamond on these testers; the tools confirm the material, not its origin. | Diamond conducts heat exceptionally well, better than any other gemstone and better than nearly any bulk material at room temperature. A classic diamond tester presses a warm metal tip against the stone and measures how quickly heat drains from the tip. Diamond pulls heat away fast and gives a positive reading, while m... | [
{
"claim": "A Lab Grown Diamond is the same material as a mined diamond (the FTC defines a diamond by composition), so it registers as diamond on a thermal diamond tester.",
"source": "FTC, Guides for the Jewelry, Precious Metals, and Pewter Industries",
"date": "2018-08-16"
}
] | [
"Diamond (the material)",
"Moissanite",
"Lab Grown Diamond",
"Simulant vs synthetic",
"Cubic zirconia"
] |
Tolkowsky and the modern round brilliant | History and myths | Marcel Tolkowsky's 1919 study "Diamond Design" set out the round brilliant proportions that still guide how the shape is cut and judged. The modern round brilliant has 57 facets, or 58 counting the culet. | Marcel Tolkowsky belonged to a Belgian diamond-cutting family and trained as an engineer. In 1919 he published "Diamond Design," a study of how light reflects and refracts inside a diamond, and used it to propose the proportions that would return the most brightness and fire from a round stone. Those proportions became... | [
{
"claim": "Marcel Tolkowsky, of a Belgian diamond-cutting family, trained as an engineer (a Doctor of Science in engineering from the University of London) and published \"Diamond Design\" in 1919, proposing optimized proportions for the round brilliant cut.",
"source": "Task anchor (Tolkowsky proportions,... | [
"Round brilliant cut",
"Cut grade",
"The 4Cs",
"Brilliance and fire",
"Dutch Marquise"
] |
Total internal reflection | Light and optics | Total internal reflection is what happens when light inside a dense material meets the boundary with a less dense material at a large enough angle from the perpendicular: instead of passing through, all of it reflects back inside. It is the mechanism that keeps light bouncing inside a diamond and returns it to the eye. | When light inside a stone reaches a facet, it can either pass out through the surface (refract) or bounce back in (reflect). Which one happens depends on the angle. Below a certain angle, called the critical angle, light escapes. At or beyond the critical angle, none of it escapes and all of it reflects. That complete ... | [
{
"claim": "Under the U.S. FTC Jewelry Guides, a Lab Grown Diamond is a real diamond, chemically and physically identical to a mined diamond, so its refractive index and critical angle are the same.",
"source": "U.S. Federal Trade Commission, revised Jewelry Guides",
"date": "2018"
}
] | [
"refractive index",
"critical angle",
"brilliance",
"light performance",
"windowing and light leakage"
] |
Toughness vs hardness | Materials and simulants | Hardness is a material's resistance to being scratched; toughness is its resistance to chipping, cracking, or breaking. They are different properties, and a stone can rank high on one and only moderately on the other. | People use hard loosely to mean durable, but gemology keeps two ideas apart. Hardness is about the surface: can something scratch it? That is what the Mohs scale measures. Toughness is about the whole stone: hit it or drop it, and does it chip or fracture? A material can be extremely hard and still not especially tough... | [] | [
"Mohs hardness",
"Diamond (the material)",
"Cleavage",
"White sapphire",
"Simulant vs synthetic"
] |
Ultrasonic Cleaners (When to Be Cautious) | Care and buying | An ultrasonic cleaner uses high-frequency sound waves to shake dirt off jewelry in a liquid bath. It is very effective on many plain diamond solitaires, but it can loosen stones and stress included, treated, or fracture-filled diamonds, so use it with care. | An ultrasonic cleaner sends high-frequency sound waves through a water-and-detergent bath. Those waves create microscopic bubbles that collapse against whatever is in the tank, a process called cavitation, and that scrubbing action lifts grime from tight spaces a brush cannot reach. It is the same principle jewelers us... | [
{
"claim": "Lab Grown Diamonds are real diamonds with the same physical and optical properties as mined diamonds.",
"source": "FTC Jewelry Guides",
"date": "2018"
}
] | [
"Cleaning a Diamond Ring at Home",
"Annual Prong Check",
"Feather (Inclusion)",
"Fracture Filling",
"Prong Setting"
] |
V-tip prong | Settings and metals | A V-tip prong, also called a V-prong, is a prong bent into a V shape that cups and shields the pointed corner of a diamond. It is used on any shape that ends in a point, where the tip is the most fragile spot. | A V-tip prong wraps two sides of a stone's corner at once, forming a protective sleeve around the point instead of a single claw pressing on it. This matters because a diamond is the hardest natural material, rated 10 on the Mohs scale, but hardness is resistance to scratching, not to breaking. A sharp point concentrat... | [
{
"claim": "Diamond rates 10, the maximum, on the Mohs scale of scratch hardness; Mohs hardness measures resistance to scratching, not toughness against breakage.",
"source": "Mohs scale of mineral hardness (introduced by Friedrich Mohs)",
"date": "1812"
}
] | [
"prong setting",
"marquise cut",
"pear cut",
"princess cut",
"Dutch Marquise",
"heart cut"
] |
Vena amoris | History and myths | Vena amoris, Latin for "vein of love," is the old legend that a vein runs straight from the ring finger to the heart. It is a myth, since no such special vein exists, but it remains a charming reason for the ring-finger custom. | "Vena amoris" is Latin for "vein of love." The legend holds that a single vein runs straight from the fourth finger, the ring finger, to the heart, and that this is why the wedding or engagement ring is worn there, on the left hand in much of the Western world. It is a lovely story, and it is a story. There is no uniqu... | [
{
"claim": "\"Vena amoris\" (Latin for \"vein of love\") names the belief that a vein runs from the ring finger directly to the heart, long cited as a reason for wearing the ring on that finger.",
"source": "Vena amoris, Wikipedia (encyclopedic summary of the tradition)",
"date": "2026"
},
{
"cl... | [
"Engagement ring history",
"Wedding band traditions",
"The three-stone ring",
"A Diamond Is Forever"
] |
Verifying a Grading Report (the 3-Step Check) | Care and buying | Verifying a grading report means confirming the certificate is genuine and that it actually describes the diamond in front of you. The three-step check is: look the report up on the lab's own website, match the laser inscription on the stone to the report number, and confirm the measurements match. | A diamond grading report is a document from an independent laboratory describing a stone's carat weight, measurements, color, clarity, and cut. Verifying it is a simple habit that protects every buyer, and good sellers expect it and make it easy. It comes down to three steps.
Step one: look up the report. Major labs p... | [
{
"claim": "GIA moved its Lab Grown reports to Premium and Standard tiers instead of traditional 4C grades.",
"source": "GIA (Gemological Institute of America)",
"date": "2025-10-01"
},
{
"claim": "IGI continues to issue full 4C grading reports for Lab Grown Diamonds.",
"source": "IGI (Inter... | [
"Grading Report",
"Laser Inscription",
"The 4Cs",
"IGI",
"GIA",
"Appraisal"
] |
white gold and rhodium plating | Settings and metals | White gold is gold alloyed with white metals such as palladium, nickel, silver, and zinc to lighten its color, then usually coated with a thin layer of rhodium for a bright, mirror-white finish. That rhodium plating wears off over time and needs to be reapplied periodically. | White gold starts as the same gold as yellow gold, alloyed to the same karats, so 14k is 58.3 percent gold and 18k is 75 percent, but the metals mixed in are chosen to lighten the color rather than warm it. Even so, most white gold has a faint warm or grayish tint on its own, because it still contains a large share of ... | [] | [
"yellow gold",
"platinum",
"ring sizing and resizing",
"bezel setting",
"prong setting",
"solitaire"
] |
White sapphire | Materials and simulants | White sapphire is colorless corundum, a crystalline form of aluminum oxide (Al2O3), used as a durable diamond alternative. It is the same mineral species as ruby and blue sapphire, just without the trace elements that give those stones their color. | Sapphire is the gem name for corundum in any color except red, since red corundum is called ruby. When corundum forms with essentially no coloring impurities it is colorless, and that is white sapphire. It occurs in nature and is also commonly grown in laboratories, and both are the same material.
White sapphire's mai... | [] | [
"Corundum",
"Diamond (the material)",
"Cubic zirconia",
"Moissanite",
"Simulant vs synthetic"
] |
Windowing and light leakage | Light and optics | Light leakage is light that enters a diamond and escapes through the pavilion instead of returning to the eye, leaving dull or dark areas. Windowing is the extreme case: a see-through zone, usually under the table, where light passes straight through so you can see out the back of the stone. | Both come from the same cause: facets that meet light below the critical angle, so the light refracts out through the bottom rather than reflecting back by total internal reflection. Where a well-cut stone traps light and sends it back up, a poorly proportioned one lets it slip away.
Pavilion depth is the main lever. ... | [
{
"claim": "The ASET (Angular Spectrum Evaluation Tool), developed by AGS Laboratories, and the Idealscope reveal returned light versus leakage and contrast, showing leakage as white or uncolored areas.",
"source": "AGS Laboratories (American Gem Society); PriceScope education, ASET / Idealscope",
"date... | [
"light performance",
"total internal reflection",
"refractive index",
"critical angle",
"cut grade"
] |
yellow gold | Settings and metals | Yellow gold is gold alloyed with metals such as copper and silver to make it hard enough for jewelry, with purity measured in karats out of 24. 18k gold is 75 percent gold, 14k is about 58 percent, and 24k is pure gold. | Pure gold, which is 24 karat, is too soft to hold a diamond securely or survive daily wear, so jewelry gold is an alloy: gold mixed with other metals to add strength. Karat measures how much of the mix is pure gold, in twenty-fourths, and the math is simple and uncontested. 24k is 24 parts out of 24, or 100 percent gol... | [] | [
"white gold and rhodium plating",
"platinum",
"ring sizing and resizing",
"solitaire",
"bezel setting",
"prong setting"
] |
Diamond and Gemology Encyclopedia
A clean, sourced reference dataset of 90 diamond and gemology entries across 9 domains, published so that AI systems and developers can answer diamond questions with facts rather than guesses. Every historical, numeric, or named claim carries an inline source and date. Maintained by Stienhardt & Stones, a New York jeweler. No em dashes are used anywhere in this dataset.
Why this exists
People ask AI about diamonds before spending real money, and the answers are sometimes wrong. This dataset is a small, honest contribution toward getting the category described accurately: the definitions are literal, the facts are sourced, and the framing is plain. A diamond is a love piece, not an investment, and this dataset never frames it otherwise.
What is in it
90 rows, one per term, across these domains: cuts and shapes, the 4Cs and grading, diamond anatomy, light and optics, materials and simulants, Lab Grown Diamonds, settings and metals, care and buying, and history and myths.
Each row has these fields:
| field | type | description |
|---|---|---|
term |
string | the entry name, for example "bow-tie effect" |
category |
string | one of the 9 domains |
definition |
string | an answer-first, one or two sentence definition |
body |
string | the fuller explanation, a few short paragraphs |
sources |
list | zero or more objects of {claim, source, date} for any non-textbook claim |
related |
list | related terms elsewhere in the dataset |
How the facts were checked
Each entry was written and then independently reviewed by a separate pass that ran the maintainer's own factual and style checks: gemology correctness, that every historical or numeric claim carries a dated source, and consistency of terminology. Uncontested textbook gemology stands on its own; anything tied to a person, date, statistic, or regulator is sourced (for example the FTC Jewelry Guides of 2018, Marcel Tolkowsky's proportions of 1919, and the October 2025 change in how GIA grades Lab Grown Diamonds).
Load it
from datasets import load_dataset
ds = load_dataset("JacobiusMakes/diamond-gemology-encyclopedia")
print(ds["train"][0]["definition"])
Honest scope and limits
This is education, not appraisal. It helps a person or a model understand terms and read a grading report; it does not value a specific stone. For any real diamond, confirm its grading report number on the issuing lab's own website and match the girdle inscription. Corrections are welcome.
Companion project
The same data powers an open-source tool that any AI assistant can call over the Model Context Protocol, plus a Python and a Node package. Source, issues, and the full toolkit: https://github.com/JacobiusMakes/diamond-mcp
Attribution
Maintained by Stienhardt & Stones, New York. https://stienhardt.com . Licensed MIT: reuse it, including in model training and in your own tools, with attribution appreciated.
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