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MIT OpenCourseWare http://ocw.mit.edu
12.001 Introduction to GeologySpring 2008
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Silicate ion (SiO44–)
The silicate ion forms tetrahedra
Oxygen ions (O2–) Silicon ion (Si4+)
Quartz structure
Figure by MIT OpenCourseWare.
Mineral Chemical formula
Cleavage planesand number of
cleavage directions
1 plane
Silicatestructure
Isolatedtetrahedra
Specimen
Olivine (Mg, Fe)2SiO4
Images removed due to copyright restrictions.
Isolated tetrahedra (soro- and nesosilicates)
Olivine group: forsterite-fayalite solid solution
Images removed due to copyright restrictions.
Mineral Chemical formula
Cleavage planesand number of
cleavage directions
1 plane
Silicatestructure
Isolatedtetrahedra
Specimen
2 planes at 90°Single chains
Olivine
Pyroxene (Mg, Fe)SiO3
(Mg, Fe)2SiO4
Images removed due to copyright restrictions.
Mineral Chemical formula
Cleavage planesand number of
cleavage directions
1 plane
Silicatestructure
Isolatedtetrahedra
Specimen
2 planes at 90°Single chains
2 planes at 60°and 120° Double chains
Olivine
Pyroxene (Mg, Fe)SiO3
Amphibole
(Mg, Fe)2SiO4
Ca2(Mg, Fe)5Si8O22(OH)2
Images removed due to copyright restrictions.
Single chains of tetrahedra
Pyroxene group
Images removed due to copyright restrictions.
Double chains of tetrahedra
Amphibole group
Images removed due to copyright restrictions.
Mineral Chemical formula
Cleavage planesand number of
cleavage directions
1 plane
Silicatestructure
Isolatedtetrahedra
Specimen
2 planes at 90°Single chains
2 planes at 60°and 120° Double chains
1 plane Sheets
Olivine
Pyroxene (Mg, Fe)SiO3
Amphibole
Micas
(Mg, Fe)2SiO4
Ca2(Mg, Fe)5Si8O22(OH)2
Muscovite:KAl2(AlSi3O10)(OH)2
Biotite:K(Mg, Fe)3AlSi3O10(OH)2
Images removed due to copyright restrictions.
Sheets of tetrahedra (phyllosilicates)
Mica group
Images removed due to copyright restrictions.
Mineral Chemical formula
Cleavage planesand number of
cleavage directions
1 plane
Silicatestructure
Isolatedtetrahedra
Specimen
2 planes at 90°Single chains
2 planes at 60°and 120° Double chains
1 plane Sheets
Olivine
Pyroxene (Mg, Fe)SiO3
Amphibole
Micas
Feldspars
Orthoclase feldspar:KAlSi3O8
Plagioclase feldspar: (Ca, Na) AlSi3O8
2 planes at 90° Three-dimensionalframework
(Mg, Fe)2SiO4
Ca2(Mg, Fe)5Si8O22(OH)2
Muscovite:KAl2(AlSi3O10)(OH)2
Biotite:K(Mg, Fe)3AlSi3O10(OH)2
Images removed due to copyright restrictions.
3-D frameworks of tetrahedra (tectosilicates)
Feldspar group
Images removed due to copyright restrictions.
ANORTHITE
CaAl2Si2O8
ORTHOCLASE
KAlSi3O8
ALBITE
NAlSi3O8
Feldspars
10
20
30
40
50
400 800 1200 1600 2000Temperature oC
coesite
lowquartz
high quartz
liquidtr. crist.
stishovite
60
70
80
Pres
sure
[kba
rs]
Rose-colored nanofibers cause the color in rose quartz: George Rossman, CalTech
Courtesy of George R. Rossman. Used with permission.
