CHAPTER 2 Matter and Minerals
52
Mineral/Formula
Cleavage
Silicate Structure
Olivine group
(Mg, Fe) 2 SiO 4
None
Single tetrahedron
Pyroxene group
(Augite)
(Mg,Fe)SiO 3
Two planes at
90°
Single chains
Amphibole group
(Hornblende)
Ca 2 (Fe,Mg) 5 Si 8 O 22 (OH) 2
Two planes at
60° and 120°
Micas
Biotite
K(Mg,Fe) 3 AlSi 3 O 10 (OH) 2
One plane
Olivine
Augite
Hornblende
Biotite
Muscovite
Quartz
Potassium
feldspar
Sheets
Double chains
Muscovite
KAl 2 (AlSi 3 O 10 )(OH) 2
Feldspars
Potassium feldspar
(Orthoclase)
KAlSi 3 O 8
Plagioclase
(Ca,Na)AlSi 3 O 8
Two planes at
90°
Three-dimensional
networks
Quartz
SiO 2
None
Example
FIGURE 2.24 Common silicate minerals. Note that the complexity of the silicate structure increases from top to bottom. (Photos by
Dennis Tasa and E. J. Tarbuck)