in hand sample. Cross sections are dark between crossed polars. 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. The blue color blueschists is due to the presence of this blue amphibole. Specimens Glaucophane is named from its typical blue color (in Greek glaucophane means " blue appearing "). of blue. Hornblend : Hornblende . Distinct pleochroism: X= colorless, pale blue, yellow; Y= lavender-blue, bluish green; Z= blue, greenish blue, violet. Orthopyroxenes are noted for having low, first-order interference colors. If the interference colors compound the sample is length slow, if they subtract the sample is length fast. Click on the image to see a larger image with a rollover of cross polars. From RRUFF. has a parallel extinction when viewed under cross polars. ... anomalous blue interference colors. The muscovite alteration products are easily visible here, but the Mg-rich chlorite is not so visible because of its low birefringence. The mica flakes show obvious mottled 2nd order interference colors .The epidote grains are hard to pick out in XP light • Color: Blue • Pleochroism: From blue to violet. The interference colors of clinozoisite are anomalous, ranging from anomalous first order Berlin blue and brown for Fe-poor varieties, to anomalous first order lemon yellow for Fe-rich ones. Glaucophane has length slow, riebeckite length (blue tourmaline is darkest w/ c-axis perpendicular to vibration direction Epidote is a common … Hypersthene : Hypersthene . Associated with lawsonite, pumpellyite, chlorite, albite, quartz, jadeite, and members of epidote group. Glaucophane crystallizes in the monoclinic system. To the left is a photomicrograph of glaucophane. This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle. The two endmembers are indistinguishable in hand specimens and are strongly pleochroic. Note the characteristic ~120 degree cleavage angles in some sections and the brown to green. Muscovite sample W-12 in cross-polarized light. Glaucophane is a sodium magnesium iron aluminium silicate hydroxide mineral, found in blueschist facies subduction zones. Sillimanite The slender prismatic crystals show high relief and are colourless in plane polarized light (left). of polarizer). Note the anomalous blue-gray interference colors in the glaucophane in this slide. Darkest when c-axis parallel to vibration direction of lower polarizer Photomicrograph of glaucophane in plain polarized Note the parallel extinction of one of the crystals and the end on view of The blue color blueschists is due to the presence of this blue amphibole. Darker with increasing Fe content. Blue in color under regular lighting, and often found in differing shades It is pleochroic in tints of brown. Click on the image to see a pleochroism rollover. On the reflection image (left below), the muscovite appears dark due to the light absorption of the minerals deeper in the section (glaucophane) It appears with brilliant interference colors throughout the thin section. In XP light the chlorite shows anomalous interference colors, the glaucophane shows 2nd order interference colors, in places somewhat masked by the blue color of the mineral. Glaucophane is also found in eclogites that have undergone retrograde metamorphism.[1]. It, along with the closely related mineral riebeckite are the only common amphibole minerals that are typically blue. As the major mineral component, it is glaucophane's color that gives the "blueschist" metamorphic rock type its name. Brittle. Light blue in thin section. Click on the image to see a pleochroism rollover. Although it has a micaceous structure, it is so easily deformed, that crystals are rarely seen. Note the anomalous blue-gray interference colors in the glaucophane in this slide. Hornblende Note the characteristic ~120 degree cleavage angles in some sections and the brown to green. http://rruff.geo.arizona.edu/doclib/hom/glaucophane.pdf, http://webmineral.com/data/Glaucophane.shtml, "Glaucophane: Glaucophane mineral information and data", "International Mineralogical Association - Commission on New Minerals, Nomenclature and Classification", https://en.wikipedia.org/w/index.php?title=Glaucophane&oldid=982503696, Creative Commons Attribution-ShareAlike License, slender long prisms, Massive granular to columnar, nα = 1.606 - 1.637 nβ = 1.615 - 1.650 nγ = 1.627 - 1.655, This page was last edited on 8 October 2020, at 15:22. the thickness of the slide by comparison with the standard interference colors for quartz and plagioclase. Glaucophane is pleochroic and both blue and blue-green colors are transmitted, depending on the crystal's orientation. In one of the slides there is an irregular-shaped mineral of a light brown color and cut by intersecting cracks. When the stage is rotated 90 degress, glaucophane's color changes from lavender to a clear, whitish purple. Alex Strekeisen - I vetrini della mia fantasia. Rio Oremo, Chiavolino, Pollone, Biella Province, Piedmont, Italy Field of View: 8 mm I believe the amphibole has been etched out of calcite. • Relief: Moderate. And interference colors depend on grain orientation, so different grains of the same mineral in one thin section normally display a range of interference colors. Glaucophane is named for its typical blue color. Blue pleochroism in thin section/grain mount distinguishes Glaucophane forms a solid solution series with ferroglaucophane (Na2(Fe,Mg)3Al2Si8O22(OH)2). Ferroglaucophane is similar to glaucophane but is slightly denser and hence increased specific gravity. Different minerals display different ranges of interference colors, so color variation is a useful tool for mineral identification. There is also a rare amphibole called holmquistite, chemical formula Li2Mg3Al2Si8O22(OH)2, which occurs only in lithium-rich continental rocks. Characteristics. light. Muscovite: The muscovite, transparent on a transmission image is a major mineral in this rock sample. Glaucophane is the magnesium-rich endmember and ferroglaucophane is the iron-rich endmember. NOR-281 Glaucophane generally forms in blueschist metamorphic rocks of gabbroic or basaltic composition that are rich in sodium and have experienced low temperature-high pressure metamorphism such as would occur along a subduction zone. The blue color is very diagnostic for this species. Basal sections will show symmetric extinction, with elongate sections displaying parallel extinction and length slow. Interference colors are first order gray to white, like quartz and feldspar. Anomalous interference colors: blue and brown. chlorite schist pyrite; Chlorite_schist; Chlorite is the organization name for approximately 10 related minerals.However, the time period Chlorite may be used each to explain the organization in fashionable, or as a specific term to explain any inexperienced member of the Chlorite institution whose precise identity isn’t always realistic to be decided. Parting on {100}, conchoidal to uneven fracture. Uniaxial/Biaxial: Uniaxial (-) Optic axial angle (2V): – - Glaucophane Subgroup: Alkali Amphiboles, formed in Na-rich environments, associated with subduction zone chemistry Distinguishing Features: 120° cleavage Moderate to high relief Biaxial Medium interference colors Fibrous habit Photomicrograph of glaucophane in an eclogite under plain polarized light, showing distinct color and 120° cleavage. Distinguished from other amphiboles by distinct blue color the glaucophane grades over into a green hornblende. light. As the major mineral component, it is glaucophane's color that gives the "blueschist" metamorphic rock type its name. Interference color: Order I (black, gray to white). Note the anomalous blue-gray interference colors in the glaucophane in this slide. Note the varying shades of blue that are observed in plain polarized Glaucophane: Rare with characteristic blue color Sphene/leucoxene: Minor Jadeite (CPX): Abundant — forms radiating aggregates with lawsonite. Uniaxial/Biaxial: Biaxial (+) Optic axial angle (2V): 2V measured: 58 – 83°, calculated: 74 – 88° Glaucophane [Na 2(Mg,Fe)3Al2Si8O22 (OH)2] is a sodic amphibole that characterizes the subduction-related blue-schist facies. Roll over image is the same photomicrograph in cross polarized Plane/cross-polarized light, field width is 1.2 mm. In hand specimen it is dark brown to black in color and shows the characteristic amphibole cleavage. IG16-36 Pyroxenes Omphacite in a glaucophane schist.€ Omphacite is an Na-Ca-Mg-Al pyroxene, and is the location of some of the albite component in this feldspar-free rock. • Cleavage: Typical amphibole cleavage intersect at about 58° and 122°. Glaucophane Note the anomalous blue-gray interference colors in the glaucophane in this slide. When the stage is rotated 90 degress, glaucophane's color changes from lavender to a clear, whitish purple. The anomalous interference colors are the result of strong dispersion of the 2V. For many years, holmquistite was mistaken for glaucophane, as the two look identical in thin section. from other amphiboles. There is no twinning in glaucophane. Extinction angle: Parallel / 0° / straight Twins: Apatite twins are rare. Lavender blue, blue, dark blue, gray or black. light yellowish violet, wine yellow, yellowish green, pale yellow, or colorless. To the left is a photomicrograph of glaucophane, the lavender colored mineral. Do the measurements on more than one grain. pleochroism. Riebeckite is the name used for minerals of the glaucophane-crossite-riebeckite series in which iron is predominant over magnesium and aluminum. In thin-section, glaucophane is distinct due to its purple-blue-yellow trichroism. Glaucophane also Anthophyllite is distinguished from … Riebeckite ... and show very low order interference colors due to its low birefringence. The blueschist metamorphic facies gets its name from abundant blue minerals glaucophane and lawsonite. Click the thumbnail to see a rollover image of the bird's eye texture when the crystal is close to extinction. Amanda Nyren (06), Bridget Mahoney (MHC '06), Camille Dywer ('14). Glaucophane [Na 2 (Mg,Fe) 3 Al 2 Si 8 O 22 (OH) 2] is a sodic amphibole that characterizes the subduction-related blue-schist facies. Interference color: Order II Extinction angle: 36 – 45° Twins: Twins with {100} as twin-plane are known. fast. Photomicrograph in plane polarized light showing lavender blue pleochroism. It is more commonly euhedral than quartz in plutonic rocks. Glaucophane is the name of a mineral and a mineral group belonging to the sodic amphibole supergroup of the double chain inosilicates, with the chemical formula ☐Na2(Mg3Al2)Si8O22(OH)2. light. To the left is a photomicrograph of glaucophane. The relief is high, and the interference colors are of the third or fourth 349 Blackish-blue fibrous aggregate of glaucophane crystals,Cazadero, Sonoma County, California, USA. Glaucophane's hardness is 5–6 and its specific gravity is approximately 3–3.2. Tends to The blue color is very diagnostic for this species. 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. Maximum interference colors are first order red or second order blue, with decreasing order correlating to decreasing Fe content. Glaucophane, along with the closely related mineral riebeckite, to which it forms a series with, and their intermediate crossite, are the only well known amphiboles that are commonly blue. The Mineral glaucophane Glaucophane is named from a combination of the Greek words Glaukos, meaning "blue", and Phainelein, meaning "appearance", alluding to its bluish color. The blue color is very diagnostic for this species. Inclined extinction. In thin section, it shows high relief with a characteristic green - brown - yellow pleochroism. Photomicrograph in plane polarized light with the stage rotated 90 degrees from above picture. Talc has the chemical formula - Mg 3 Si 4 O 10 (OH) 2. Characteristic of high-pressure, low-temperature regional metamorphic rocks (blue schist). Lawsonite: Abundant — Colorless, tabular, medium birefringence, parallel extinction. It is probably best know for its low hardness. Glaucophane crystals are named from the Greek 'to appear blue', and fine translucent blue crystals are highly collectable. In Greek, glaucophane means "blue appearing". In Greek, glaucophane means "blue appearing". Cross polarized light, 100x. Glaucophane is named for its typical blue color. The interference color chart is the same one as in the third edition 18 years earlier; now, however, it is no longer tipped in, but has been bound in, with the unfortunate consequence of losing the center portion of the chart (lost is the birefringence interval between 0.021 and 0.023) (Figure 18). Glaucophane: Glaucophane . pleochroism. Glaucophane - Na 2 Mg 3 Al 2 Si 8 O 22 (OH) 2. Crocidolite is called the "Blue Asbestos", because it is strongly pleochroic, ranging from Prussian blue and indigo blue to yellow green. • Interference colors: Low, from I order to II order. Glaucophane in a blueschist.€ As with most monoclinic amphiboles, glaucophane has birefringent colors in the lower second order. Glaucophane forms a series with the less-common Ferro-glaucophane, where Glaucophane is the magnesium-rich end member and Ferro-glaucophane is the iron-rich end member. Talc. Color: Blue Gray: Hardness: 6-6.5: Specific gravity: 3.1 to 3.2: Cleavage/fracture: Two perfect prismatic {110}/ uneven: Luster: Vitreous: Transparency: Transparent to translucent: Streak: White to very light blue: δ: 0.01 – 0.02: PPL: Colorless to blue or violet Often strongly pleochroic: XPL: Up to 2 nd order interference colors Interference color may be masked by mineral color