12.001 Introduction to Geology Spring 2008 For information ... · Pyroxene (Mg, Fe)SiO 3 Amphibole...

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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.