Chemical formulae:
SiO4
In PPL quartz is barely different to Feldspar. Quartz is usually a little cleaner looking than K-Feldspar, which often has tiny grainy inclusions in it. (Sericite Alteration or fine grained Muscovite with High Alteration Colours) and Plagioclase usually has good cleavage visible in XPL and similar tiny grainy inclusions. (Which may be epidote.)
Quartz is often confused with K-Feldspar, Plagioclase, Nepheline and Cordierite. See here for a good outline of the differences
Property
|
|
Twinning
|
No
|
Extinction
|
Undulose
|
Colour
|
Colourless in ppl
|
Relief
|
Very low
|
Pleochroism
|
No
|
Habit
|
Tabular, Prismatic
|
Birefringence
|
In PPL quartz is barely different to Feldspar. Quartz is usually a little cleaner looking than K-Feldspar, which often has tiny grainy inclusions in it. (Sericite Alteration or fine grained Muscovite with High Alteration Colours) and Plagioclase usually has good cleavage visible in XPL and similar tiny grainy inclusions. (Which may be epidote.)
Quartz is often confused with K-Feldspar, Plagioclase, Nepheline and Cordierite. See here for a good outline of the differences
Quartz in Plain Polarised Light
Quartz in Cross Polarised Light
Quartz Extinct in Cross Polarised Light
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