Glaucophane. Plane-polarised light, width of view 2.5 mm. Lavender blue, blue, dark blue, gray or black. Glaucophane - Na 2 Mg 3 Al 2 (Si 4 O 11) 2 (OH) 2 Glaucophane, From the Greek (glaukos) for "sky-blue" and (phainestai) "to appear" in allusion to its colour, belongs to the Glaucophane-riebeckite-crossite series; Ideal glaucophane, Na 2 Mg 3 Al 2 (Si 4 O 11) 2 (OH) 2, forms at least … Characteristic of high-pressure, low-temperature regional metamorphic rocks (blue schist). light. There is no twinning in At St. Marcel, Val d’Aosta, and Alex Strekeisen - I vetrini della mia fantasia. In Japan, at Ubuzan, This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle. The Glaucophane mineral is named after two Greek words: glaukos, which means “bluish green”; and phainesthai, which means “to appear.” Specimens can be gray, lavender blue, or bluish black. Glaucophane is the magnesium rich member and ferroglaucophane is the iron rich member. Glaucophane in Turkish blueschist Glaucophane in Greek blueschist (the two samples on the left) Fine-grained blueschist Medium-grained blueschist Garnet-studded retrograde blueschist after eclogite. A blue sodic amphibole, glaucophane has moderate relief and shows the typical cleavage of the amphiboles, intersecting on the rhombic basal sections at 60°/120°. 14 - Minerals in Thin Section-University of North Carolina 15 - Minerals in Thin Sections-Humboldt State 16 - Online Mineral Museum 17 - QUT Mineral Atlas 18 - Ruff.Info 19 - UCLA - Petrography Thin-Sections 20 - WWW-MINCRYST. Parting on {100}, conchoidal to uneven fracture. Glaucophane crystallizes in the monoclinic system. Glaucophane has To the left is a photomicrograph of glaucophane, the lavender colored mineral. On Anglesey, Wales. Check out the thin section scans. Green varieties usually have X= light yellow green, Y=green or grey-green and Z=dark green. Home Rocks and Minerals Plagioclase Feldspar (thin section) Reference URL Share . Cleavage: Perfect parallel to {100}, less … Ranges, as on the Tiburon Peninsula and at Vonsen Ranch, Marin Co., at Glaucophane, common amphibole mineral, a sodium, magnesium, and aluminum silicate that occurs only in crystalline schists formed from sodium-rich rocks by low-grade metamorphism characteristic of subduction zones. Darkest when c-axis parallel to vibration direction of lower polarizer Color: Dark green to black, greenish-brown, more rarely lighter green. Relief: High positive Habit/Form: Kyanite commonly forms elongate bladed or columnar crystals that may appear to be bent. greenish blue, violet, Measured: 10° to 80°, Calculated: Significant deposits have been discovered in Greece (Cyclades Islands, Syra Island), Italy (St. Marcel, Val d'Aosta, Piollore), Wales (Anglesey), Australia, Japan, and the US (Kodiak Islands, California). length slow, riebeckite length fast. Note the varying shades of blue that are observed in plain polarized Further Reading. Glaucophane Ridge, Panoche Valley, San Benito Co., and near Valley Ford, Sonoma Colour: Grey to lavender-blue. This mineral exhibits a characteristic blue color with distinct pleochroism from colorless to lavender blue when viewed in thin section by plane-polarized light. Glaucophane in Thin Section Although commonly light yellow-green in thin section, it may be colorless. Alex Strekeisen - I vetrini della mia fantasia. cross polars. Lavender blue, blue, dark blue, Glaucophane is defined as a member of the glaucophane group with Mg>Fe 2+ in the C 2+ position and (OH) in the W position. 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 ☐Na2Si8O22(OH)2. Prehnite - Ca 2 (Al,Fe 3+)[AlSi 3 O 10](OH) 2 Named in 1788 by Abraham Gottlieb Werner in honor of the Dutch Colonel, Hendrik von Prehn, who is credited with discovering the mineral in 1774 at the Cape of Good Hope in South Africa. Description: This rock was used in Open University level 3 course on igneous and metamorphic rocks. Co.; in the Kodiak Islands, Alaska, USA. Glaucophane also has a parallel extinction when viewed under Chlorite: Property: Value: Comments: Formula (Mg, Al, Fe) 3 (Si,Al) 4 O 10 (OH) 2. It is a glaucophane schist from the Isle of Tinos, Greece. Plane-polarised light, field of view 1 mm. At numerous sites in the California Coast The pleochroic mineral changes colors from yellow to violet to blue when a thin section is viewed in plane polarized light. glaucophane in thin section FKM-100 XP - YouTube. Formula: (Ca,Na,K) 2-3 (Mg,Fe,Al) 5 (Al,Si) 8 O 22 (OH,F) 2. XPL. Pleochroic in various shades of green and brown. (2020). Its interference colors commonly seem anomalously bright compared to pyroxenes, possibly a result of the high dispersion of the 2V. For many years, holmquistite was mistaken for glaucophane, as the two look identical in thin section … Island, Cyclades Islands, Greece. 1.650 nγ = 1.627 – 1.655. perpendicular to vibration direction of polarizer). This facies forms from material caught under subduction zones in mountain belt regions. Outcrops of glaucophane-rich metamorphic rocks are commonly blue and tend to have good foliation; these rocks are termed blueschists. The thin section contains coarse grained glaucophane, talc, … The procedure for checking Becke lines is summarized in the video (Figure 2.6.1) at the start of this chapter. Roll over image is the same photomicrograph in cross polarized Significant deposits have been discovered in Greece (Cyclades Islands, Syra Island), Italy (St. Marcel, Val d'Aosta, Piollore), Wales (Anglesey), Australia, Japan, and the US (Kodiak Islands, California). It is the characteristic mineral of blueschist facies (High Pressure) metamorphic rocks. Glaucophane forms a solid solution series with ferroglaucophane; Na 2 (Fe, Mg) 3 Al 2 Si 8 O 22 (OH) 2. For many years, holmquistite was mistaken for glaucophane, as the two look … glaucophane in thin section FKM-100 XP - YouTube. Glaucophane is also found in eclogites that have undergone retrograde metamorphism. Distinguished from other amphiboles by distinct blue color Color: Colorless to pale blue; violet blue (thick section), cobalt blue (thick section) Pleochroism: None to weak (violet-blue, deep cobalt blue). To link to this object, paste this link in email, IM or document To embed this object, paste this HTML in website. Lustre: Vitreous. fast. Blue pleochroism in thin section/grain mount distinguishes from other amphiboles. of polarizer). Photomicrograph of glaucophane in plain polarized Glaucophane in Hand Sample. from other amphiboles. Glaucophane is characteristically pleochroic in shades of blue and purple. When iron replaces the magnesium in its structure, it is known as ferroglaucophane. Distinct pleochroism: X= When the stage is rotated 90 degress, glaucophane's color changes from lavender to a clear, whitish purple. Blue pleochroism in thin section/grain mount distinguishes has a parallel extinction when viewed under cross polars. Glaucophane occurs in schists formed by high-pressure metamorphism of sodium-rich sediments at low temperatures (up to 400°F/200°C) or by the introduction of sodium into the process. Widespread in some mountain belts. Name: From the Greek for bluish green and to appear. In PPL a thin section of Hornblende ranges from yellow -green to dark brown. Distinctively, glaucophane shows blue-lilac pleochroism. 62° to 84°, nα = 1.606 – 1.637 nβ = 1.615 – Characteristic of the blueschist facies, in The pleochroic mineral changes colors from yellow to violet to blue when a thin section is viewed in plane polarized light. This optical mineralogy/petrography video is part of the "video atlas of minerals in thin section" library at https://www.rockptx.com. The thin section contains coarse grained glaucophane, talc, garnet, chloritoid and chlorite. It is rarely fibrous. Ferroglaucophane is similar to glaucophane but is denser, generally darker in color with a diminished pearly luster. On Syra Glaucophane is named from a combination of the Greek words Glaukos, meaning "blue", and Phainelein, meaning "appearance", alluding to its bluish color.Glaucophane forms a series with the less-common Ferro-glaucophane, where Glaucophane is the magnesium-rich end member and Ferro-glaucophane is the …