introduction to the silicate mineralsepsc352.wustl.edu/2019_files/labs/introsilicates.pdf ·...
TRANSCRIPT
![Page 1: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/1.jpg)
Introduction to the Silicate Minerals
Earth Materials – EPSc 352
19/24/2019
![Page 2: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/2.jpg)
The culprit: [SiO4]4- tetrahedron
29/24/2019
![Page 3: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/3.jpg)
Mineral StructuresMinerals are classified on the basis of Si-O polymerism
Nesosilicates
[SiO4]4- Isolated tetrahedra
Examples: olivine, garnet
Sorosilicates
[Si2O7]6- Double tetrahedra
Examples: lawsonite, epidote
Cyclosilicates
n[SiO3]2- n = 3, 4, 6
Examples: benitoite BaTi[Si3O9]
axinite Ca3Al2BO3[Si4O12]OH
beryl Be3Al2[Si6O18] 39/24/2019
![Page 4: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/4.jpg)
Mineral StructuresMinerals are classified on the basis of Si-O polymerism
Inosilicates
[SiO3]2- [Si4O11]
4-
Single chains Double chains
pyroxenes/pyroxenoids amphiboles49/24/2019
![Page 5: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/5.jpg)
Mineral StructuresMinerals are classified on the basis of Si-O polymerism
Phyllosilicates
[Si2O5]2- sheets of tetrahedra
Examples: mica, talc, clays, serpentine
59/24/2019
![Page 6: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/6.jpg)
Mineral StructuresMinerals are classified on the basis of Si-O polymerism
Tectosilicates
[SiO2]0
3D framework of tetrahedra, fully polymerized
Examples: quartz, feldspars, feldspathoids, zeolites69/24/2019
![Page 7: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/7.jpg)
NesosilicatesIsolated tetrahedra
79/24/2019
![Page 8: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/8.jpg)
NesosilicatesIsolated tetrahedra
89/24/2019
![Page 9: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/9.jpg)
NesosilicatesIsolated tetrahedra
99/24/2019
Garnet
X3Y2(SiO4)3
![Page 10: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/10.jpg)
NesosilicatesIsolated tetrahedra
109/24/2019
![Page 11: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/11.jpg)
SorosilicatesDouble tetrahedra
119/24/2019
Hemimorphite
Zn4Si2O7(OH)2·H2O
![Page 12: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/12.jpg)
CyclosilicatesDouble tetrahedra
129/24/2019
Beryl
Be3Al2Si6O18
![Page 13: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/13.jpg)
InosilicatesChains of tetrahedra
139/24/2019
Augite (Pyroxene)
(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6
![Page 14: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/14.jpg)
InosilicatesChains of tetrahedra
149/24/2019
Hornblende (Amphibole)
Ca2(Mg, Fe, Al)5 (Al, Si)8O22(OH)2
![Page 15: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/15.jpg)
InosilicatesChains of tetrahedra
159/24/2019
Cleavage angles can be interpreted in terms of weak bonds in M2
sites (around I-beams instead of through them)
Narrow single-chain I-beams → 90o cleavages in pyroxenes while wider
double-chain I-beams → 60-120o cleavages in amphiboles
![Page 16: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/16.jpg)
PhyllosilicatesSheets of tetrahedra
169/24/2019
Muscovite
KAl2(AlSi3O10)(F,OH)2
![Page 17: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/17.jpg)
Serpentine
179/24/2019
Octahedra are a bit larger than
tetrahedral match, so they cause
bending of the T-O layers (after
Klein and Hurlbut, 1999).
Antigorite maintains a
sheet-like form by
alternating segments of
opposite curvature
Chrysotile does not do
this and tends to roll into
tubes
![Page 18: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/18.jpg)
Tectosilicates3D framework of tetrahedra
189/24/2019
AlbiteNaAlSi3O8
![Page 19: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/19.jpg)
Tectosilicates3D framework of tetrahedra
199/24/2019
Quartz Polymorphs
![Page 20: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/20.jpg)
Tectosilicates3D framework of tetrahedra
209/24/2019
Quartz Cristobalite
Tridymite Coesite
![Page 21: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/21.jpg)
Streak
Density
Color
Hardness
Cleavage
9/24/2019 21
Identification of SilicatesHand Sample
![Page 22: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/22.jpg)
• Color of the mineral when it’s powdered
• Not helpful for most silicates
• Powder is usually white
• Some silicate minerals are harder than streak plate
9/24/2019 22
Identification of SilicatesStreak
![Page 23: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/23.jpg)
• Usually darker-colored silicates are denser (this is not always true)
• e.g., garnet • Use a few silicate minerals of known density
for comparison purposes
9/24/2019 23
Identification of SilicatesDensity
![Page 24: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/24.jpg)
• Be careful about use of color
• Only useful in some specific cases (e.g., specific shades of green – olivine,epidote)
• For Fe-Mg silicates (e.g., olivine), the darker the color, the more Fe in it
9/24/2019 24
Identification of SilicatesColor
![Page 25: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/25.jpg)
• Silicate minerals are mostly harder than non-silicates, but very few of them are harder than quartz
• Quartz hardness = 7
• Kyanite: Al2SiO5, interesting example• Displays greatly different hardness properties along
different directions
9/24/2019 25
Identification of SilicatesHardness
![Page 26: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/26.jpg)
• Silicate minerals are mostly harder than non-silicates, but very few of them are harder than quartz
• Quartz hardness = 7
• Kyanite: Al2SiO5, interesting example• Displays greatly different hardness properties along
different directions
9/24/2019 26
Identification of SilicatesHardness
![Page 27: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/27.jpg)
• Cleavage is defined as the tendency of a crystal to break along a plane in certain definite directions
• A good feature to use to distinguish among the silicates (e.g., amphibole and pyroxene)
9/24/2019 27
Identification of SilicatesHardness
![Page 28: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/28.jpg)
9/24/2019 28
![Page 29: Introduction to the Silicate Mineralsepsc352.wustl.edu/2019_Files/Labs/IntroSilicates.pdf · 2019-09-30 · Narrow single-chain I-beams →90o cleavages in pyroxenes while wider double-chain](https://reader033.vdocuments.net/reader033/viewer/2022042318/5f07ffc67e708231d41fd2a9/html5/thumbnails/29.jpg)
9/24/2019 29
Presentation inspired by slides from:• Molly C. McCanta (University of Tennessee, Knoxville)• John D. Winter (Whitman College, now retired)