WebTwins in longitudinal section may resemble twins seen in plagioclase but thin sections may be stained to distinguish cordierite from the feldspars. Twins are more likely in cordierite from high grade metamorphic rocks than in medium-grade rocks. Optic Sign: Biaxial (+ or -) Rarely biaxial (+). 2V: 35-106° Mostly biaxial (-) with 2V between 40 ... http://www.maas.edu.mm/Research/Admin/pdf/21.%20Dr%20Ni%20Ni%20Win(227-238).pdf
How the composition of minerals in a thin section can be determined …
WebPlagioclase commonly shows this type of twinning, called the Albite Twin Law, with {010} as the twin plane. Such twinning is one of the most diagnostic features of plagioclase. ... If during the alteration process a thin crust of a new mineral forms on the surface of a preexisting mineral, then the preexisting mineral is removed, leaving the ... WebIn thin section, plagioclase feldspar grains often look like they’re sprinkled with dirt (PPL) or tiny confetti (XPL). You can find the explanation on the plagioclase feldspar page. Oligoclase in Hand Sample Stay tuned! Oligoclase in Thin Section Stay tuned! Further Reading Oligoclase at mindat.org Oligoclase at webmineral.com skyway rmc plants private ltd
Plagioclase - University of North Dakota
WebGeneral Plagioclase Information Chemical Formula: (Na,Ca) (Si,Al)4O8 Composition: Molecular Weight = 270.77 gm Sodium 4.25 % Na 5.72 % Na 2 O Calcium 7.40 % Ca 10.36 % CaO Aluminum 9.96 % Al 18.83 % Al 2 O 3 Silicon 31.12 % Si 66.57 % SiO 2 Oxygen 47.27 % O ______ ______ 100.00 % 101.48 % = TOTAL OXIDE Empirical Formula: Na 0.5 Ca 0.5 Si 3 AlO 8 WebIn thin sections, the An content of plagioclase can be well determined finding extinction angles on Carlsbad-albite twins combination or symmetrical extinction on albite twins in appropriately... WebOrthoclase is often confused with quartz - try looking for cloudy patches on individual crystals in plain polarized light which indicate weathering of the crystal. And check to see … skyway roofing ct