ERTH 2104 Study Guide - Quiz Guide: Iddingsite, Pleochroism, Pyroxene

• School: Carleton University
• Department: Earth Sciences
• Course: ERTH 2104
• Professor: Brian Cousens

Document Summary

Cracked, brownish-red, iddingsite alteration, clear pebbly look in thin section, pointed terminations. Pyroxene: square, green to brown, 2 good cleavages but usually poor expressed. Square, slight green colour, no pebbly look, may see cleavage (orthopyroxene: clear) Commonly ri(cid:373)(cid:373)ed (cid:271)y/(cid:272)o(cid:374)(cid:448)erted to (cid:858)opa(cid:272)ite(cid:859) (cid:449)here a(cid:373)phi(cid:271)ole has dehydrated. Plagioclase: white-grey, rarely blue(labordorite), polysynthetic twinning on one cleavage plane. Twinning, low birefringence, usually elongate, zoning, sieve texture (lots of holes- new feldspar created around as it changes) Biotite: grey-black, thin, mica cleavage, lustre of cleavage plane, K-feldspar: pink, grey, greenish, carlsbad twin (1 side black/1 white), perthitic texture. Carlsbad twins, crosshatch twinning in plutonic varieties, low birefringence, commonly turbid. Very low birefringence, elongate shape, commonly look like shadow. Clear, high relief, embayed, lots of tiny inclusions. Quartz: clear to grey, glassy, commonly with biotite in plutonic rock b/c formed together @ same time. High relief, radiation damage (dark edge) around crystals, high birefringence that is.