Ge 101. Introduction to Geology and Geochemistry
Lecture 2
Crystal Structure of Minerals
Image 2.1
Mineral Chemical formula
Cleavage planesand number of
cleavage directions
Silicatestructure Specimen
1 plane Isolatedtetrahedra
2 planes at 90°Single chains
2 planes at 60°and 120° Double chains
1 planeSheets
Olivine
Pyroxene
Amphibole
Micas
Feldspars
2 planes at 90°Three-dimensional
framework
(Mg,Fe)2SiO4
(Mg,Fe)SiO3
Ca2(Mg, Fe)5Si8O22(OH)2
Muscovite:KAl2(AlSi3O10)(OH)2
Biotite:K(Mg, Fe)3AlSi3O10(OH)2
Orthoclase feldspar:KAlSi3O8
Plagioclase feldspar: (Ca, Na) AlSi3O8
Image 2.2