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#ThinSectionThursday It's all quartz in today's rock, an Upper Cretaceous pure quartz-sandstone from the Lochaline sand mine. This particular sample is quite well-cemented together by syntaxial quartz overgrowths on the older round quartz grains. You can see the ghostly round grain boundaries of the original sedimentary grains. New quartz has then grown with the same crystal orientation around each grain, turning the loose sand into sandstone. Field of view 2mm across. 🤩

#Geology #Microscopy

A view of a rock thin section using plane polarized light under a polarizing microscope. Almost all the image is made of a clear, transparent mineral, with faint ghostly outlines of rounded grains visible within it. There are some darker bubbles in the section which "stand out" from the background - these are an artefact of sample preparation.

A view of a rock thin section using crossed polars under a polarizing microscope. The image consists of black, grey cream and white polygonal grains. Each of these contains a faint ghostly outline of a smaller, rounded grain visible within it. There are some darker bubbles in the section which "stand out" from the background - these are an artefact of sample preparation.

T.S. Thursday! Mantle xenolith (dunite) infiltrated by mafic melt on the left side. The melt has crystallized clinopyroxene, as shown by this electron backscattered diffraction image. Each pixel's data is a diffraction pattern that can determine mineral. By Bill Menarik. #thinsectionthursday

#ThinSectionThursday In Archaean times, ultra-hot komatiite lavas were often erupted at Earth's surface. The hottest ones were much hotter than anything erupted today (maybe up to 1600oC). They often show fabulous "spinifex" textures with skeletal/dendritic crystals typical of very rapid growth, like this 2.7 billion year old one from Munro Township, Ontario. Field of view about 2mm wide. Specimen in the #Hunterian museum, University of Glasgow. See Alt-txt for more. 🤩 #Geology #Microscopy

A view of a rock thin section taken down a polarizing microscope using crossed polars. The view consists mostly a long, feathery, rainbow-coloured crystals (clinopyroxene) in a matrix of fine-grained dark brown material, with two larger, long linear crystals of greyer mineral (serpentinized olivine) running NNE-SSW at the left and right sides of the view.

A view of a rock thin section taken down a polarizing microscope using plane-polarized light. The view consists mostly of long, fine feathery, pale brownish crystals (clinopyroxene) in a matrix of fine-grained dark brown material, with two larger, long linear crystals of greyer mineral (serpentinized olivine) running NNE-SSW at the left and right sides of the view.

Thin Section Thursday! Ophitic texture of plagioclase laths encased in clinopyroxene in a gabbro from the Glen Mtns. Layered Complex in southwestern Oklahoma. Contributed by Robert Puckett. You can contribute too! Send images to akoziol1 at udayton dot edu. #thinsectionthursday

#ThinSectionThursday Here's a volcanic rock done right 🤩 🥰 This is a trachyte from the Canary Islands. with a gloriously
diverse pheno(?)cryst assemblage: K-feldspar, nepheline, titanite, zircon, apatite, clinopyroxene AND amphibole (+opaque oxides). Field of view about 2mm wide.

#Geology #Microscopy #Mineralogy #igneousPetrology

A view of a rock thin section taken using plane polarized light under a polarizing microscope. The rock consists of a fine-grained pale brownish turbid material, with diverse kinds of larger crystals sitting in it. At the bottom left sits a large pale brown lozenge, looking very intense. Abofe this on the left is a patch of intensely brown and green mineral, intergown with clear crystals. Elswhere paler green, and clear crystals can be seen.

A magnesium-rich basalt retrieved by the Apollo 12 mission from the Moon. brightly coloured pyroxene and olivine surround grey plagioclase in cross-polars.

This photo was taken in 2003 from a travelling collection of thin sections sponsored by NASA.

#ThinSectionThursday #Apollo12 #Moon #Basalt #NASA

A thinsection imaged in cross-polarized light. Brightly colored pyroxene and olivine grains surround gray laminated plagioclase feldspar. field of view ~1mm. Sample 12005.

#ThinSectionThursday Fabulous 🪶 feathery🪶 symplectite textures in this Lewisian gneiss from the south slopes of Roneval, South Harris. Pink garnet & green clinopyroxene formed during early, hot, high pressure granulite facies metamorphism have reacted during later decompression/hydration to produce zones of finely intergrown amphibole, plagioclase, and opaque magnetite. View ca 2mm across. Tasty! 😋 🥰

#Geology #Metamorphism #Coronas #Microscopy

@mineralsocamerica.bsky.social

A view of a rock thin section photographed using a polarizing microscope using plane polarized light. The central lower part of the image is mostly occupied by a large pale pink, clear crystal, while the top of the image, plus the extreme left and right are mostly occupied cloudy greenish crystals. Betwenn the pink crystal and the green crystals is a zone of finely intergrown, feathery-looking mixture of green and colourless minerals, with black grains concentrated at the edge against the green material.

T.S. Thursday! Large rounded grains of garnet surrounded by masses of muscovite mica and biotite mica. Also found are small, brown oval-shaped grains of tourmaline. By Larry Tuttle, U Maine Farmington. Send images and short caption to akoziol1 at udayton dot edu. #thinsectionthursday

Eclogite with a blueschist overprint from the Franciscan complex of California #ThinSectionThursday

Learn more about eclogite: https://en.wikipedia.org/wiki/Eclogite

Learn more about blueschist: https://en.wikipedia.org/wiki/Blueschist

A photograph of a rock thin section. A round crystal of pink garnet is in the middle of the image. The bottom left has green omphacitic pyroxene and the top right has blue glaucophane that formed after the pyroxene.

Thin Section Thursday! This megacryst of orthopyroxene shows high relief and faint pleochroism in PPL. Cross the polars, & the crystal comes alive with abundant thin bands of exsolution lamellae of clinopyroxene. Contributed by Matt Kohn. #thinsectionthursday

#ThinSectionThursday A beautiful low-grade metamorphic rock from the southern Highlands today: the rock consists of large clear (grey/white) porphyroblasts of untwinned albite set in a foliated matrix of green (very dark) flakes of chlorite, and clear flakes (rainbow colours) of muscovite. Field of view about 2mm across. #Geology #Microscopy

See Alt text for more info.

A microscope view of a rock thin section using plane polarized light. The view shows many large clear blocky crystals sitting in a background of smaller, soft green and transparent flakes. The flaky minerals are aligned across the view, with some small folds.

A microscope view of a rock thin section using crossed polars.. The view shows many large greysih blocky crystals sitting in a background of smaller, dark and rainbow-tinted flakes. The flaky minerals are aligned across the view, with some small folds.

A graded bed and the start of the next one in a Silurian greywacke, Appalachians. The mostly quartz and plagioclase grains get finer to the left, indicating that 'up' was to the left as the grains settled in the water column.

#ThinSectionThursday #Geology #Sediment #Quebec

A thin section imaged in plan-polarized light. The big clear grains are quartz, and get finer to the left, before abruply coarsening again. The original 'up' was to the left.

Garnet lawsonite blueschist from the Franciscan subduction complex. #ThinSectionThursday

Learn more about lawsonite: https://en.wikipedia.org/wiki/Lawsonite?wprov=sfla1

Learn more about the Franciscan complex:
https://en.wikipedia.org/wiki/Franciscan_Complex?wprov=sfla1

#Geology

A photograph of a garnet lawsonite blueschist thin section in plane polarized light. The image shows a large (2 mm) white lawsonite porphyroblast and smaller (1 mm) pink garnet porphyroblast in a fine grained (<500 um) matrix of light blue glaucophane.

Photomicrograph (crossed polars, gypsum plate inserted) of a slate (metamorphic rock). Mineral grains shown include actinolite amphibole, biotite mica, quartz, & plagioclase feldspar. FOV: 5 millimeters (mm). Contributed by Christopher Houdeshell, U Maine Farmington. #thinsectionthursday

#ThinSectionThursday Here's a (Palaeogene?) hyaloclastite made of altered basaltic glass + calcite, plus a few colourless plagioclase crystals, from an oil exploration borehole in the Atlantic, W of Shetland. This is a rock that sounds like it should be horrible, but I think it's beautiful 🤩 😊 The former glass is now altered to greenish smectitic clay minerals, which show their zoned fibrous crystalline habit in the second (crossed polars) image . Field of view 2mm wide. #Geology #Microscopy

A view of a rock thin section taken down a microscope using plane polarized light. The rock consists of banded green and green-brown material, with colourless patches, and elongate crystals.

A view of a rock thin section taken down a microscope viewed between crossed polars. Most of the rocks consists of dark, green and brown banded material, showing fibres at right angles to the bands, plus a pale green-with-pink-spots patch at the upper right, and a couple of grey-and-black elongate striped crystals.

#ThinSectionThursday Here's a chonky big roundish crystal of zircon sitting happily in this Palaeoproterozoic metasedimentary gneiss from the Leverburgh Belt, in South Harris. Field of view 2mm wide.

Rock sample in the superb Hunterian museum collections at the University of Glasgow.

A view of a rock thin section down a polarizing microscope, using plane polarized light. A large, rounded, intense greyish transparent crystal looms intensely in the centre of the view with some irrregular opaque black mineral grains to the right, and a fine-grained intergrowth of colourelss, brown, black and green mineral grains on the left. The rest of the image is occupied by blandly colourless mineral grains.

A view of a rock thin section down a polarizing microscope, between crossed polars. A large, rounded, intense green crystal looms intensely in the centre of the view with some irrregular opaque black mineral grains to the right, and a fine-grained intergrowth of white, grey, and black mineral grains on the left. The rest of the image is occupied by blandly black grey and white mineral grains.

#ThinSectionThursday Rockall may be a tiny wee lonely rock, but it's made of an exceptionally interesting granite with amazing peralkaline chemistry, ultra rich in barium and zirconium, for example. Here's a thin section (FOV 2mm wide) from the Hunterian Museum collections showing cloudy colourless (grey) perthitic feldspar, clear colourless (grey-black) quartz and large pale green-brown (rainbow) zoned aegirine crystals. 🤩 😋 I would love to land on Rockall! #Geology #Rockall

A view of a rock thin section, using plane polarized light usgin a polarizing microscope. The is a large squareish colourelss, turbid crystl at the top of the field of view. The rest of the view is occupied by pale green-to-brown crystals with cracks running along their length, and some clear colourless mineral.

A view of a rock thin section down a polarizing microscope between crossed polars. There is a large squarish mottled grey crystal at the top of the field of view, half-embedded in an elongate purple crystal below, flanked by green-purple crystal on either side. The spaces between these bright crysla are filled with black and grey material.

Rare blue yoderite replacing kyanite (-talc + quartz). Only found in two places on Earth (Tanzania and Zimbabwe), yoderite forms at high pressure in hot subduction zones from rocks rich in in Mg and Al, poor in alkalis and Ca, in the presence of water and oxidized ferric iron (±Mn).

Named after Hat Yoder of the Geophysical Lab, CIW.

#ThinSectionThursday #Yoderite #Kyanite #Whiteschist #Subduction #CarnegieInstitutionWashington #Tanzania #Zimbabwe

Blue yoderite ( Mg(Al,Fe3+)3(SiO4)2O(OH) ) surrounding remnant kyanite with talc and quartz. Plane polarized transmitted light.

Yoderite surrounding remnant kyanite with talc and quartz. Cross polarized transmitted light.

Thin Section Thursday: The matrix of devitrified glass and microlites has flowed around this large composite feldspar grain. In XP, the central grain is black because it has been rotated to extinction. In other orientations it is gray to white. Contributed by Matt Kohn. #thinsectionthursday

Thin Section Thursday! Large crystals of feldspar and quartz scatter across a groundmass of devitrified glass and microlites. In XP, the feldspars display spectacular twinning and zoning. Contributed by Matt Kohn. #thinsectionthursday Send images and a caption to akoziol1 at udayton dot edu.

#ThinSectionThursday

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