ERTH 2404 Lecture Notes - Gneiss, Chert, Amphibolite
3 Mar 2014
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Amphibole: black, not shiny, prismatic cleavage, hexagonal crystals, grey streak v. Calcite: reaction with acid, scratched by penny, vitreous, white streak, rhombohedral habit. Chalcopyrite: metallic, dark brassy yellow, scratched by fingernail, greenish black streak v. Flourite: scratched by penny, purple/blue crystals, octahedral cleavage, pyramid habit, white streak v. Galena: metallic, cubic cleavage and habit, scratched by steel nail, grey or black, heavy. Garnet: adamantine, v. hard, white streak, dodecahedral habit. Magnetite: magnetic, grey or black, v. hard, black streak v. Mica: scratched by fingernail, thin sheets layers, prismatic habit, vitreous. Olivine: v. hard, glassy, green crystals, white streaks, granular v. Plagioclase feldspar: polysynthetic twinning, v. hard, white streak and colour, vitreous. Potassium feldspar: perthitic texture, contrasting between pink and white, rhombohedral habit, white streak v. Pyrite: fool"s gold, yellow/bronze, v. hard, greenish black streak. Pyroxene: vitreous, scratched by steel nail, black, grey/green streak, square crystals v. Talc: light, greasy, rubs off, silky, white streak.
