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Small phlogopite laths in highly deformed sample from Siilinjärvi apatite ore. Photomicrograph from thin section in cross and plane polarised light.
Amphibole fragments in mica groundmass in a thin sample from Siilinjärvi apatite ore. Photomicrograph in cross and plane polarised light.
Etched and stained thin section. Photomicrograph from thin section in cross and plane polarised light: the brighter mineral grains in the picture are dolomites, and the darker ones calcite grains.
Scanned image of thin section from Siilinjärvi apatite ore M3 in cross polarised transmitted light. <p>The thin section can be divided into two domains: about half of the area consists of carbonate domains and rest of mica domains. The mica domains are sheared and have a nematoblastic texture. The shearing is also visible in the carbonate domains, but not that clearly. The carbonate domains show heterogranular texture. Feldspars are found as rare accessory mineral. </p><p>Carbonates form 50 area-% of the sample and they are grouped into domains that are as wide as the whole section and consist almost purely of carbonates. Calcite is slightly more common carbonate mineral than dolomite, and some veins consist only of calcite. The grain size varies quite lot, the biggest grains are &gt; 2 mm in diameter and smallest ones well &lt; 0.1 mm. The grains are moderately altered and slightly elongated to the mica shear direction. The grains are rounded and the aggregates have a granular texture. </p><p>Common phlogopite flakes form 45 area-% of the thin sections. The grains are very elongated and some mica fishes are present. The grains are commonly &lt; 0.1 mm wide and the average grain is 0.3 mm long. The grains are oriented in the same direction as the different domains in the sample. The mica domains are not as monomineralic as the carbonate domains, because apatite, carbonate and opaque grains are also present. </p> Most of the apatite in the sample occurs in small carbonate-apatite veins inside the mica domains, and the mineral forms 5 area-% of the sample. The grains are quite small (less than 0.3 mm in diameter) and rounded. Some individual apatite grains are also present in the phlogopite rich zones. Apatite is not present in the carbonate domains.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. The sample was collected from the Särkijärvi area, from the shear zone in the central-northern end of the pit. <p>The thin section has a hypidiomorphic structure. Sheared zones comprise 20 area-% of the thin section. The rock is only slightly oriented. </p><p>Tetraferriphlogopite forms the weak orientation in the thin section, and about 75 area-% of the thin section. Tetraferriphlogopite flakes have turned into the shear direction and broken into elongated grains towards the shear direction. The biggest grains are on average 2.5 mm long and 1.5 mm wide. The large mica flakes are bent. </p><p>Amphiboles cover 12 % of the thin section and occur as sub- to anhedral monoclinic grains. The grains are broken and have a lot of inclusions: big inclusions (about 1 mm in width) of apatite and mica, and smaller (less than 0.1 mm in width) inclusions of carbonates. Occasionally, the amphibole grains are altered from the sides. The biggest poikiloblastic grains are &gt; 10 mm wide, but the grain size varies a lot. The blue colour of the mineral grains is quite weak, but still prominent – the amphiboles are a mixture between tremolite and richterite. </p><p>Apatite is present in quite small rounded porphyroclasts (usually less than 1 mm wide), the bigger grains are often associated with carbonates. Apatite forms about 10 area-% of the thin section. Large grains have inclusions of carbonates and tetraferriphlogopite. </p> Carbonates are mostly found as inclusions in apatites and amphiboles. Both carbonate minerals are equally common. They form 3 area-% of the thin section. The carbonate inclusions are elongated in amphibole grains, but in apatite grains the boundaries between carbonates are hard to distinguish.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>The thin section has lepidoblastic texture and the big grains form about 75 area-% of the thin section. Sheared zones comprise the rest 25 area-% of the thin section. </p><p>Phlogopite forms the orientation in the thin section, and about 60 area-% of the thin section. According to pleochroism, the phlogopite is not common phlogopite nor tetraferriphlogopite, the composition is between those minerals. The phlogopite flakes have turned into the shear direction and broken into elongated grains towards the shear direction. The biggest grains are on average 4 mm long and 1.5 mm wide. C’-type shear band cleavage is visible and bigger mica grains are bent. </p><p>Apatite forms about 30 area-% of the thin section and occurs as big, rounded grains. The biggest grains are on average 5 mm wide, but they are broken into smaller pieces along the shear direction. The small pieces are commonly grouped. Apatite grains, especially the bigger ones, are full of carbonate inclusions. The apatite fractures are filled with carbonates. The carbonate-filled veins are often oriented to opposite direction to mica shear direction. The broken individual pieces of apatite are in companion with mica in the shear zones, but mostly the apatite forms big zones composed mainly only of apatite and carbonates. </p> Carbonates are often found in company with apatite and form about 10 area-% of the thin section. Calcite is more common carbonate mineral than dolomite. Anhedral granoblastic grains are often about 0.3-0.5 mm wide and grouped with other carbonate grains. Much of the calcite is found in the cracks within the apatites. The calcite in the apatite cracks has a veined shape. Individual grains of subhedral dolomite are found outside apatite-carbonate areas.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>The sample is highly sheared, and the shearing in concentrated into micas. Almost the whole sample show a flow structure, the only exception is a carbonate mineral domain in the other side of the thin section. </p><p>Common phlogopite forms 70 area-% of the thin section. The mineral has deformed and sheared to small elongated flakes. Some larger grains has remained, but mostly the mica is found as small elongated chips. The average grain size is hard to specify because it varies so much, but commonly the elongated chips at the shear zones are about 0.3 mm long and less than 0.1 mm wide. </p><p>Richterite amphiboles are concentrated into one vein-like structure which cross-cuts the thin section. The amphiboles form 15 area-% of the thin section and the subhedral grains are usually quite big (up to 4 mm in diameter), but broken into smaller pieces. The grains have a lot of inclusions. </p><p>Carbonates are not that common in the thin section, but calcite has formed a vein-like structure in the other side of the thin section. The texture of the structure is granular and it consist dominantly of carbonates. The grain size is on average 1 mm in diameter. The phlogopite has penetrated this structure from the sides, and in these spots apatite is present. Some pieces of calcite occur in the flow zones, but it is not that abundant. Carbonates form 10 area-% of the thin section. </p> Pieces of apatite are found all over the sample, but they are more frequent near the richterite grains. The large apatite grains are filled with some small inclusions. Apatite forms 5 area-% of the thin section. The grain size is usually quite small, but some non-broken grains are &gt; 1 mm in diameter.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>The thin section presents apatite-rich carbonate ore. The grain size is quite big and the thin section consist mostly of big apatite grains in granular carbonate mass. The sample is not oriented. The grains are mostly anhedral. </p><p>Carbonates form the groundmass in the sample and 55 % of the thin section area. Calcite is more common carbonate mineral than dolomite. Carbonates form mineral aggregates with granoblastic texture, and the grain size varies in the sample. Dolomite grains are commonly smaller than calcite grains. The biggest grains are 3 mm in diameter. The grains in the aggregates are less than 1 mm in diameter, and regionally the grains in the aggregates can be less than 0.2 mm in diameter. </p><p>Apatite is present as large porphyroclasts that form 30 area-% of the thin section. Rouded grains are commonly slightly elongated, and have some carbonate inclusions which are oriented along the fractures planes. Grain diameter varies normally between 1 and 4 mm. </p> Tetraferriphlogopite forms 15 area-% of the thin section. Grains are usually large, but some broken pieces are also present. The biggest flake is 8 mm long and 2 mm wide, while the average grain is about 2 mm long and 1 mm wide.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>The thin section has a well-developed foliation and plenty of apatite. The thin section is highly sheared, and the mineral grains have shattered to small fragments. Shearing has concentrated to the mica-rich zones. </p><p>Common phlogopite is present as uniformly oriented elongated laths. Bigger flakes are almost completely broken into pieces, but some grains still remain in the apatite rich zones. Lots of mineral fragment, mostly apatite, are found in the mica flow area, apart from the most powerful shear zones. Common phlogopite forms half of the thin section area and the grains vary in size with the shearing intensity. Usually the elongated grains are 0.1-0.5 mm long, and less than 0.1 mm wide. </p><p>Apatite covers 35 % of the thin section and is present almost all over the thin section. It is commonly in contact with carbonates, but much of the apatite is also as individual fragments in the mica groundmass. The biggest grains, though already broken, are &gt; 5 mm in diameter. More common is the size of the fragments, 0.1-0.5 mm in diameter. </p> Carbonates form 15 area-% of the thin section, and both carbonate minerals are present. Calcite is more common in contact with the apatite grains, and dolomite as small scale aggregates in the mica flow. Carbonate grains are &lt; 0.5 mm, often 0.05-0.2 mm in diameter.
Scanned image of thin section R625 110.80-110.95 in cross polarised transmitted light, Siilinjärvi apatite ore. <p>The thin section is carbonate rich and consists mainly of granular carbonate aggregate with some mica and apatite porphyroclasts. </p><p>Carbonates cover 75 % of the thin section and form the groundmass of the thin section. Calcite is the dominating carbonate mineral in the thin section, and dolomite grains are often smaller than the calcite grains. The texture is polygonal and the grains in the carbonate aggregates are on average 0.5 mm in diameter. The largest grains are just over 1 mm wide and smallest are &lt; 0.1 mm. In general, the carbonates are well-preserved and non-altered, but some veins have metamorphic aureoles. There is also a spot where carbonates and micas have been pulverised to fine mass. </p><p>Common phlogopite forms 13 area-% of the thin section and is present as a couple of broken porphyroclasts and fragments. The biggest grain is 7 mm in diameter, but fragments can be &lt; 0.1 mm in diameter. The average flake is about 1 mm wide and rounded. The fragments are often lath-shaped. The laths and other elongated grains are oriented in the same direction. </p> Apatite is present as large porphyroclasts in the carbonate groundmass. The rounded grains are 1-8 mm in diameter and have inclusion trails of carbonates. Apatite forms 12 % of the thin section area.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>The thin section has a clear orientation and the movement has concentrated to planes between the bigger grains. Clasts form half of the thin section, and the rest is composed of oriented groundmass. </p><p>Tetraferriphlogopites are present as bent flakes and elongated laths. The flakes have turned into the shear direction and broken into elongated grains towards the shear direction. Groundmass-sized fragments constitute about 60 % of the micas. The flakes are 0.5-2.5 mm in diameter and have often signs of deformation: they are bent and broken by the cleavage plains. The laths are shattered, and grain size varies with the shearing intensity from flake-sized grains to extremely tiny groundmass. Tetraferriphlogopite covers 70 % of the thin section. </p><p>Apatite is present as altered grains and as fragments broken from them. The grains are often in companion with carbonate minerals, and the carbonates form inclusion trails in apatite grains. Apatites occurs in all sizes: from tiny fragments &lt; 0.1 mm wide to large porphyroclasts up to 5 mm in diameter. Apatite forms 20 area-% of the thin section. </p> Carbonates form 10 % of the thin section area, and the dominating carbonate mineral is dolomite. They are found in dispersed veins with apatite and as individual grains in the flow zones. Grains are commonly 0.1-0.5 mm wide. The grains around apatites are often only &lt; 0.1 mm in diameter. Some small scale aggregates are found in veins with apatite.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. The thin section is thinner in the right hand side, and that is the reason for different interference colours there. <p>The thin section consists of apatite grains in mica groundmass. The thin section is highly sheared and mica flakes have grounded into elongated pieces. Carbonates are only featured as an accessory mineral. </p><p>Tetraferriphlogopite forms 85 % of the thin section area and it is mostly present as small elongated laths. The laths are uniformly oriented, although they circle around the apatite clasts. Some bigger flakes have survived, commonly in the shade of large apatite grains. Groundmass-sized fragments constitute about 75 % of the micas. The laths are shattered, and grain size varies with the shearing intensity. The grains are mostly &lt; 1 mm long and 0.2 mm wide, and the average grain is about 0.3 mm long and &lt; 0.1 mm wide. </p> Apatite is present as fragments and rounded grains, and covers 15 % of the thin section. Some very minor amounts of carbonates are found near or inside the apatite grains. The diameter of the apatite grains is 0.5-2.5 mm, the fragments are smaller.
Scanned image of thin section from Siilinjärvi apatite ore. Crossed polarizers. <p>The rock is oriented and porphyroclastic. The micas and amphiboles are clearly oriented, and the carbonates have grown into vein-like structures. </p><p>Tetraferriphlogopite is present as small laths and porphyroclasts of large flakes. Laths are commonly 0.2-0.5 mm long and less than 0.1 mm wide. Bigger grains are up to 3 mm in diameter, and exist unto lath-sized particles. Oriented laths form roughly 60 % of the total area of tetraferriphlogopites, and in total the mineral forms 70 % of the thin section area. </p><p>Carbonates cover 15 % of the thin section. Dolomite is more common carbonate mineral than calcite. Carbonates are found as individual grains, as granular aggregates, and in companion with apatite. Calcite occurs commonly as big aggregates, and dolomite is commonly found as individual grains. Usually the carbonate grains are quite small, but some grains in the middle of the aggregates are up to 1.5 mm in width. Average sized grain is &lt; 0.5 mm in width. Carbonates show almost no signs of alteration. </p><p>Apatite forms 10 area-% of the thin section. They are found as rounded grains, broken grains, and fragments. Bigger grains have some inclusion trails of carbonates. Grains are found in all sizes between tiny fragments and large porphyroclasts (&gt; 0.1-3 mm). </p> Richterite amphiboles are widely oriented and are found as elongated bars and euhedral lozenges. Grain size varies a lot: the biggest grains are &gt; 3 mm in diameter meanwhile many broken fragments are &lt; 0.1 mm wide. The richterite grains cover 5 % of the thin section.
Scanned image of thin section from <a href="https://en.wikipedia.org/wiki/Siilinj%C3%A4rvi_carbonatite" class="extiw" title="en:Siilinjärvi carbonatite">Siilinjärvi apatite ore</a> in cross polarised transmitted light. Actual sector size about 37 × 20 mm. <p>The thin section is only slightly oriented and shearing has barely effected to the rock. The grain size is quite large and carbonate content is high. </p><p>Tetraferriphlogopite is the main mineral of the thin section and it forms 50 % of the area. Grains are usually 1-3 mm in diameter and oval in shape. Smaller elongated chips are common between the grains. </p><p>Carbonates form one third of the thin section area. Calcite is the dominating carbonate mineral. Carbonates look unaltered in the thin section and they are grown into large mineral aggregates. Dolomite grains are commonly smaller than the calcite grains. The diameter of the grains is 0.2-2 mm. </p><p>Apatite is widespread mineral in the thin section, and usually found as big rounded grains. The grains are 0.5-2.5 mm in diameter and form 10 area-% of the thin section. </p> Amphiboles are found as variable sized sub- to euhedral grains. Biggest crystals are &gt; 3 mm in diameter, and usually they are &gt; 0.5 mm in diameter. However, even tiny crystals are found. Amphiboles form 7 area-% of the thin section.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. Actual sector size about 37 × 20 mm. <p>The thin section is only slightly oriented and shearing has barely effected to the rock. The grain size is quite large and carbonate content is high. </p><p>Tetraferriphlogopite is the main mineral of the thin section and it forms 50 % of the area. Grains are usually 1-3 mm in diameter and oval in shape. Smaller elongated chips are common between the grains. </p><p>Carbonates form one third of the thin section area. Calcite is the dominating carbonate mineral. Carbonates look unaltered in the thin section and they are grown into large mineral aggregates. Dolomite grains are commonly smaller than the calcite grains. The diameter of the grains is 0.2-2 mm. </p><p>Apatite is widespread mineral in the thin section, and usually found as big rounded grains. The grains are 0.5-2.5 mm in diameter and form 10 area-% of the thin section. </p> Amphiboles are found as variable sized sub- to euhedral grains. Biggest crystals are &gt; 3 mm in diameter, and usually they are &gt; 0.5 mm in diameter. However, even tiny crystals are found. Amphiboles form 7 area-% of the thin section.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>The thin section has a very low amount of small mica chips. The bigger mica flakes in the sample are oriented, but shearing has not affected the grain size nor formed any foliation. Magnetite is found as accessory mineral in the thin section. </p><p>Tetraferriphlogopite forms 75 area-% of the sample and is mostly present as somewhat elongated flakes. The grains are usually 1-2 mm long and 0.3-1.5 mm wide. Smaller chips are in minority and do not show any orientation. </p><p>Amphiboles look often quite broken, but usually the grains still appear large. The blue colour is quite weak, but still prominent. The amphiboles are a mixture between richterite and tremolite. The biggest grains are &gt; 7 mm in diameter and have inclusions of micas and apatites. Some smaller (diameter 0.3-1.5 mm) euhedral grains are also present. Amphiboles form 10 area-% of the thin section. </p><p>Carbonates look quite pure in the thin section and they are grown into large mineral aggregates. The aggregates have other mineral grains in them, mostly apatite. Carbonate grain size varies a lot, and the biggest grains are usually found in the middle of the granular aggregates (diameter almost 2 mm). The aggregate margins feature smaller grains. Carbonates are also quite common as small individual grains in the mica groundmass. Calcite is more common carbonate mineral in the aggregates, dolomite as individual grains. Carbonates form 8 area-% of the thin section. </p> Apatite is found in companion with carbonates and forms 7 area-% of the thin section. Mostly the apatite is present as big rounded grains together with carbonates, but there is also a lot of small apatite pieces in the mica groundmass. Average sized apatite is 1-3 mm in diameter, the pieces in the groundmass are 0.1-1 mm in diameter.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>In the thin section apatite is mostly found as big inclusions in carbonate aggregates. The thin section has also a couple of narrow carbonate veins and a clear flow structure. </p><p>Tetraferriphlogopite forms 70 area-% of the thin section. The grains are often quite broken and bent, but still, grains almost 5 mm wide are found. Small elongated chips form one third of the mica area, larger flakes two thirds. Flakes are usually 1-5 mm long, chips &lt; 1 mm and more elongated. </p><p>Apatite appears as large rounded grains in companion with carbonates and forms 10 area-% of the thin section. The grains have carbonate inclusion trails. The diameter of the grains is 1-4 mm. </p><p>Carbonates form large aggregates in the thin section and 10 % of the area. Calcite is the dominating carbonate mineral. Grain boundaries are sometimes hard to distinguish because of the dustiness of the grain surfaces and small grain size. Usually the grains are &lt; 1.5 mm in diameter, at the aggregate margins smaller than that. </p> Amphiboles form 10 area-% of the thin section, and are commonly found as small euhedral grains in the groundmass. The grains are altered into magnetite and &lt; 1 mm in diameter. A few elongated small grains and one large grain &gt; 1 cm long are also present.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>The thin section is very mica rich and lightly sheared. Shearing has shattered the mica flakes into pieces but there are spots without any broken pieces, only big mica grains. </p><p>Tetraferriphlogopite forms 82 area-% of the thin section. The flakes are usually 1-3 mm long and &gt; 0.5 mm in width. Smaller elongated pieces form one quarter of the mica area, and they are found within the shear bands. The tetraferriphlogopites are moderately oriented. </p><p>Amphiboles are mostly found near the more sheared parts of the thin section and they form 10 % of the thin section area. Some grains are euhedral but mostly they are subhedral. Inclusions are widespread and the most common inclusion mineral is tetraferriphlogopite. The amphibole grains are 1-4 mm in diameter. The blue colour of the mineral is quite weak, but still prominent – the amphiboles are a mixture between richterite and tremolite. </p> Apatite grains are often broken, but the pieces are still close to each other. The grains are 1-3 mm in diameter, although broken pieces in the mica groundmass are smaller. Apatite and carbonates are usually in companion with each other. Apatite forms 5 area-% and carbonates 2 area-% of the thin section. The carbonate grains are smaller than apatite and usually less than 1 mm in diameter. Dolomite is the dominating carbonate mineral.
Scanned image of thin section from Siilinjärvi apatite ore in cross polarised transmitted light. <p>The thin section is highly sheared and has a fine grain size. Mineral crystals have broken into small fragments, and almost only remaining structures are carbonate aggregates. Tetraferriphlogopite covers half of the thin section area and is mostly present as tiny elongated and oriented laths. The laths are usually 0.1-0.5 mm long but some bigger flakes are remaining with diameters up to 2 mm. </p><p>Carbonates are present as granular mineral aggregates but also as fine-grained mash with apatite. Calcite is the dominating carbonate mineral. The grain diameter in the aggregates is 0.2-1 mm and the grains are quite well-preserved. Outside the aggregates the grains are much smaller and in companion with apatite; these grains are commonly dolomites. Carbonates form 30 area-% of the thin section. </p><p>Apatite is mostly found as scattered small fragments. Apatite covers 15 area-% of the thin section, and is often in companion with carbonates. Fragments are mostly &lt; 0.5 mm in diameter, but some still remaining larger grains can be up to 2 mm in diameter. Usually the fragments are 0.05-0.2 mm in diameter. </p> Richterite amphiboles and opaques are featured as accessory minerals. Richterite grains are often seen as small elongated slivers or euhedral lozenges in the mica flow areas. Euhedral crystals are &lt; 0.3 mm in diameter, elongated grains can be slightly larger. Opaques are probably mostly magnetite.
Thin sections of limestone rocks (one is a coral boundstone) under an optical microscope
"C. G. S." (José Ramírez del Pozo y M. Aguilar) thin sections collection. Geological and Mining Institute of Spain: Drill Core Repository. Peñarroya, Córdoba, Spain.
Plate 5 of <b>The Early Cambrian Fossil <i>Salterella conulata</i> Clark in Eastern North America</b> <p>By Ellis L. Yochelson Contributions to Paleontology, Geological Survey <a rel="nofollow" class="external text" href="https://pubs.er.usgs.gov/publication/pp683B">Professional Paper 683-B</a>, 1970 Plate 5 caption: </p> <dl><dd>(Taken in plain transmitted light. All four figures and pl. 4, figs. 1 and 3, are from the same thin section)</dd> <dd>Figures 1-4. Thin sections of <i>SaIterella conulata</i> Clark.</dd> <dd>1. Part of thin section, a short distance below base of apertural cavity, showing central tube filled with recrystallized calcite, laminated inner deposits, and outer wall. X 100. From the upper part of the Vintage Dolomite in the kiln of a small abandoned quarry, east of the Landis Valley Farm Museum and 1,000 feet south of the intersection of Oregon Pike and Hunsecker Road, Lancaster quadrangle, Pennsylvania ; USGS locality 6021-CO. USNM 166245.</dd> <dd>2. Same specimen as figure 1, X 15.</dd> <dd>3. Lower part of apertural cavity of same specimen, x 50.</dd> <dd>4. Upper part of specimen shown to left on plate 4, figure 3, X 50 magnification.</dd></dl>
titanite, thin section with crossed polarizers, 13,5 X magnified
Tonalite. nicol paralleli
Topas im Dünnschliff im linear-polarisierten Licht in einem Topasgreisen (Erzgebirge)
Topas im Dünnschliff unter gekreuzten Polarisatoren in einem Topasgreisen (Erzgebirge)
Image of an ultra thin section of a carbonate rock . Interference colors are not consistent with those of a normal thin section.
Picture of a ultra thin section of a carbonate rock. Interference colors are different to a normal rock thin section.
Original figure caption: <i>Thin sections. (A) Grimberg. (B, C) Erwitte. (D-F) Liencres. (A-C) Wackestones contain clay and silt, with relatively low content of bioclasts. (D-F) Silty packstones with abundant bioclasts and siliciclasts.</i>
Photomicrograph of platy crystals in a metamorphic rock.
Thin section of interior hornfels of contact aureole showing garnet, cordierite, orthopyroxene in cross polarized light. Presence of orthopyroxene indicates high-grade contact metamorphism.
Yoderite (Blue) on Kyanite. Mautia Hill (Tanzania). Yoderite is a very rare mineral and Mautia Hill is the type locality for this mineral. Plane polarized light image, magnification 2x (Field of view = 7mm)