WebSep 20, 2010 · Biotite in PPL. Initially it is a light pale-brown colour. This is described as its body-colour. Note that as you turn the stage of the microscope the biotite colour changes to a dark-brown colour. http://sites.und.edu/dexter.perkins/opticalmin/birefringence.htm
ALEX STREKEISEN-Biotite-
WebGranite under PPL and XPL ... composed of Qurtz + Felspar + Biotite mica. Quartz shows Colourless, transparent and unaltered. Cleavage absent, Relief low positive, so that the outlines of the ... WebIn igneous rocks often with biotite and K-feldspar. Also in low-med grade meta rocks. Crystals in igneous rocks often rectangular laths. Often zoned: usually An-rich cores and Ab-rich rims. An-rich cores may alter more easily to sericite - a fine-grained turbid mica. Twinning distinctive - otherwise process of elimination. darth shader
(PDF) Site U1443 Netramani Sagar - Academia.edu
WebBiotite (darker in color and is pleochroic in ppl), Talc (smaller 2V), Pyrophyllite (larger 2V), birds-eye extinction and cleavage are also distinctive. Occurrence Muscovite has a widespread occurance and is … WebNov 13, 2024 · Isotropic garnet and pleochroic biotite in PPL and XPL. The biotite shows nice birdseye extinction in XPL. Video by Bryn Mawr College Geology Department. WebIn PPL a thin section of Hornblende ranges from yellow -green to dark brown. Green varieties usually have X= light yellow green, Y=green or grey-green and Z=dark green. ... Hornblende is easly confused with biotite. Distiguishing factors are the lack of birds eye extinction and the two distinct cleavages. Simple twinning is relatively common. darth severin