Microcline is identical to orthoclase in many physical properties; it can be distinguished by x-ray or optical examination; viewed under a polarizing microscope, microcline exhibits a minute multiple twinning which forms a grating-like structure that is unmistakable. When this happens, twinning usually results. Upon cooling, orthoclase must rearrange its structure from monoclinic to triclinic. Optical Properties Qti l hittQuartz is commonly white to colourless in hand speciman and colourless in thin section. Microcline (Greek - small slope) has the same chemical composition as orthoclase but is classified in the triclinic crystal system. Crystallography : Triclinic, a = 8.58, b = 12.96, c = 7.21, a = 89.7°, b = 115.97°, g = 90.87°, Z = 4; space group P1; point group 1. Uniaxial (Trigonal) positive and length fastlength fast. Add tags Comment Rate. Other, rare, related feldspar varieties include adularia and anorthoclase. The three principle varieties of K-feldspar are microcline (low temperature), orthoclase (medium temperature), sanidine (high temperature). Its chemistry and atomic arrangement are variable, so optical properties vary as well. The amateur has a few clues. To link to this object, paste this link in email, IM or document To embed this object, paste this HTML in website. Chemically very stable mineral, and with mediumwith medium-high hardness (7)high hardness (7) Download: … Microcline is the lowest temperature form of alkali feldspar. Habit : Prismatic, stubby to elongate crystals are typical. The blue-green feldspar amazonite is the only gem variety of microcline. Low relief and low 1st order birefringence – sometimes tin ggyed yellow. Calculated Properties of Microcline : Electron Density: Bulk Density (Electron Density)=2.54 gm/cc note: Specific Gravity of Microcline =2.56 gm/cc. Microcline (thin section) View Description. Home Rocks and Minerals Microcline (thin section) Reference URL Share . Optical Properties. The really precise way is to use thin sections to determine the optical properties along the different crystallographic axes. When viewed under a polarizing microscope, microcline exhibits a minute multiple twinning which forms a grating-like structure that is unmistakable. Microcline is identical to orthoclase in many physical properties, and can be distinguished by x-ray or optical examination. Fermion Index: Fermion Index = 0.01 Boson Index = 0.99 : Photoelectric: PE Microcline = 2.85 barns/electron U=PE Microcline x r electron = … Microcline is the stable form below about 400 C. Orthoclase and sanidine are stable above 500 C and 900 C, respectively. Optical Properties : Microcline s tartan plaid twinning (a combination of albite and pericline twinning) is its most diagnostic. Quartz is uniaxial positive with a low relief and low birefringence, thus ... Microcline. 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