Geos 306
Mineralogy of the Earth's Crust


Silica, SiO2
Quartz

Cristobalite

Tridymite

Coesite

opal, composed of spheres of tridymite or cristobalite, held together by water.


Feldspars
Albite NaAlSi3O8
K-spar KAlSi3O8
Anorthite CaAl2Si2O8
high albite (high temperature form, disordered Si/Al)
low albite (ordered Al/Si)
Microcline (ordered Al/Si)
Orthoclase (partially ordered Al/Si)
Sanidine (disordered Al/Si)
Movie showing compression of albite

Reading
Wenk & Bulakh, Chapter 19