Radiating crystals of chlorite, showing some colour zoning. Chlorite in augen gneiss, crossed polars PPL image, 10x (Field of view = 2mm) Epidote and chlorite crystals filling an amygdule. Magnification: 40x Rock: metagranodiorite Click here to watch this grai…. (Mg,Al,Fe) 3 (OH) 6 There are many compostional variations of chlorite where substitution of Mg, Al, Fe 2+ and Fe 3+ in the octahedral sheets and substitution of Al 3+ and Si 4+ in the tetrahedral sheets can occur. Cr-Mg-Al-rich chromites are realtively transparent, and can be dark-brown at full thin section thickness. Alex Strekeisen - I vetrini della mia fantasia. The grain above. PPL image, 2x (Field of view = 7mm) Epidote and chlorite crystals filling an amygdule. sphene, glaucophane and epidote). Plane-polarised light, field of view 1 mm. Scanning electron micrograph of chlorite slickensides in Brallier Formation shale, Clinochlore and laumontite in Castle Danger amygdaloidal basalt, plane polars, Clinochlore and laumontite in Castle Danger amygdaloidal basalt, crossed polars, Clinochlore and Laumontite, Crossed Polars, Chlorite with Epidote Grains, Plane Polars, Chlorite with Epidote Grains, Crossed Polars. Surrounded by sericitized feldspars. Muscovite in Thin Section Thin Section GigaPans. This optical mineralogy/petrography video is part of the "video atlas of minerals in thin section" library at https://www.rockptx.com. PPL . Chlorite: Property: Value: Comments: Formula (Mg, Al, Fe) 3 (Si,Al) 4 O 10 (OH) 2. - pale green - green, Interference colours The name chlorite encompasses a variety of Mg-rich phyllosilicates which are difficult to tell apart without detailed chemical studies. monoclinic (Fe-rich Topotactic alteration Skyros, Greece . Color: Green, yellowish green, olive green, blackish green, bluish green, white, pink. We promise that its purpose really is to give you a feel for chlorite, not to overwhelm you with incoherent information. Magnification: 100x Rock: garnet mica schist To view t…, Muscovite displaying its characteristic moderate birefringence and birdseye extinction in cross-polarized light. Fe-rich chlorite will appear blue, PPL: Green Green-brown Yellow-green Pleochroic Moderate to moderately high relief Often interspersed with other mica minerals: XPL: Low birefringence Yellow or Purple or Brown or Blue or. The crystals above Magnification: 40x Rock: Precambrian-aged basalt collected near Castle Danger, MN Cl…, Muscovite interspersed with chlorite (the brownish green pleochroic mineral) in plane polarized light. Topotactic alteration of biotite to chlorite. Trust us: once you learn to recognize it in all its many guises, you’ll never not know it when you see it. PPL. Surrounded by sericitized feldspars. Plane-polarised light, width of view 2.5 mm. What’s that stuff that looks like dirt in PPL and confetti in XPL? coloured chlorite, here as an alteration of garnet is a blueschist (with However, the term chlorite can be used both to describe the group in general, or as a specific term to describe any green member of the Chlorite group whose exact identity is not practical to be determined. System: Monoclinic. Chromite is dark-brown to opaque at full thin section thickness. Fe-rich chlorite will appear blue, often called “anomalous blue” or “Berlin blue.” δ: 0.006 to 0.020: Special properties: Chlorite is a common alteration mineral - 1st order, frequently anomalous, bright green, strongly Radiating crystals often called “anomalous blue” or Chromite is a spinel-type mineral, like magnetite, and has an extensive solid solution in the magnetite composition direction. Lustre: Greasy, Pearly, Dull. indicate a magnesium-rich variety. Density: 2.6–3.3. Anomalous 'Berlin blue' interference colours indicate an iron-rich chlorite. Muscovite, plane polars Muscovite, crossed polars ... Fine-grained muscovite with chlorite (green), PPL Muscovite and Chlorite, Plane Polars. ... 48 Lawsonite Lawsonite, pale brownish, with glaucophane, chlorite and white mica, in blueschist. Magnification: 40x Rock: metagranodiorite Click here to watch this grai…, Chlorite after biotite in cross polarized light. Magnification: 40x Rock: Metagranodiorite Click here to watch these grains r…, Chlorite after biotite in plane polarized light. chlorite, with a subhedral crystal of sphene (centre). Magnification: 40x Rock: Precambrian-aged basalt collected near Castle Danger, MN Cl…, Clinochlore and the zeolite mineral laumontite in cross polarized light. under crossed polars, showing anomalous blue and violet interference colours. The information below, then, may seem a bit scattered and/or vague. and biotite, Chlorite slickensides in Brallier Formation shale Magnification: 40x Rock: Metagranodiorite Click here to watch these grains r…, Two large chlorite grains peppered with epidote grains in cross polarized light. 'Berlin blue' interference colours indicate an iron-rich chlorite. Chlorite in Balls Bluff siltstone Magnification: 100x Rock: garnet mica schist…, Two large chlorite grains peppered with epidote grains in plane polarized light. Rock-forming minerals of metamorphic rocks, in thin section (a work in progress) 1 Olivine: forsterite Olivine: Forsterite, in marble. PPL image, 10x (Field of view = 2mm) Epidote and chlorite crystals in an altered trachyte. Chlorite schist, crossed polars Chlorite with muscovite and quartz, crossed polars PPL . Biotite altering to Clinochlore and laumontite in Castle Danger amygdaloidal basalt, plane polars Chlorite #1 thin section (hFOV 2mm) The feldspars alter to sericite, which is a catch-all name for fine-grained white mica whose identity can’t be pinned down just by looking at a thin section. The field of view Formula: (Mg,Fe) 3 (Si,Al) 4 O 10 (OH) 2 • (Mg,Fe) 3 (OH) 6. Epidote and chlorite crystals in an altered trachyte. of biotite to chlorite. Chlorite porphyroblasts in either Popes Head Formation schist or Station Hills phyllite (there is some argument about this one) The grain above. PPL. Chlorite in augen gneiss, plane polars Sometimes a mix. Hardness: 2–2½. Clinochlore and laumontite in Castle Danger amygdaloidal basalt, crossed polars, Clinochlore and the zeolite mineral laumontite in plane polarized light. Chlorite with muscovite and quartz, plane polars of chlorite, showing some colour zoning. The crystals above under crossed polars, showing anomalous blue and violet interference colours. The anomalous brown colours of the chlorite Chlorite in Castner marble, Chlorite schist, plane polars “Berlin blue.”, Commonly occurs with muscovite -; Mg-rich +), Colour - colourless XPL . Common variations include clinochlore, pennine, prochlorite, and chamosite. Muscovite interspersed with chlorite (the brownish green pleochroic mineral) in plane polarized light. Chlorite - (Mg,Fe 2+,Fe 3+,Mn,Al) 12 [(Si,Al) 8 O 20](OH) 16 Chlorite is the group name for about 10 related minerals. Anomalous above under crossed polars. Scanning electron micrograph of chlorite slickensides in Brallier Formation shale XPL. This chlorite grain is surrounded by sericitized feldspars.