UNIVERSITY OF SOUTH ALABAMA
GY 302: Crystallography &
Mineralogy
Lecture 22: Inosilicates 2
Amphiboles
Last Time (online)
Class VIII Minerals: Inosilicates (part 1)
1.
General Introduction to Inosilicates
2.
Pyroxenes
3.
Pyroxenoids
Inosilicates
The “chain” silicates come in 2 main “flavors”
Single chains (Si:O = 1:3)
(Pyroxene Group)
(Pyroxenoid Group)
Double chains (Si:O = 1:2.5)
(Amphibole Group)
Inosilicates (single chain)
Inosilicates (single chain)
Two major sub groups of pyroxenes
are distinguished on the basis of
crystal structure:
1) Orthopyroxenes (orthorhombic)
2) Clinopyroxenes (monoclinic)
http://www.uwgb.edu/dutchs/GRAPHIC0/ROCKMIN/ATOM-STRUCT/PyroxChain.gif
Inosilicates (single chain pyroxenes)
General formula: XYSiO3 or XY(Si,Al)2O6
X[larger ions] = Ca2+, Na+, Fe2+ and/or Mg2+; rarely Zn2+, Mn2+, Li+
Y[smaller ions] = Cr3+, Al3+, Fe3+, Mn3+
Monoclinic
Orthorhombic
Si:O ratio is 1:3
(octahedrally coordinated
cations between SiO3 chains
produce orthorhombic or
monoclinic symmetries)
http://ruby.colorado.edu
Inosilicates (pyroxenoids)
General formula: X2SiO3
X[larger ions] = Ca2+, Na+, Fe2+ and/or Mg2+
http://ruby.colorado.edu
Si:O ratio is 1:3
(larger cations force triclinic
symmetry)
Inosilicates (single chain)
Orthopyroxene: orthorhombic minerals
(5)
Hypersthene, Enstatite, Ferrosilite, Donpeacorite,
Nchwaningite
Clinopyroxene: monoclinic minerals
(18)
Clinoenstitite, clinferrosilite, pigeonite, diopside,
hedenbergite, spudomene
Pyroxenoid: Triclinic minerals (lots)
wollanstonite, pectolite, rhodonite
Inosilicate Minerals (orthopyroxene)
your textbooks “mineral” (p265)
Orthopyroxenes
hyperstene
http://upload.wikimedia.org/wikipedia/en/4/42/Pyrox_names.png
http://ruby.colorado.edu/~smyth/min/images/enstatite.gif
Enstitite is actually one member of a
continuous series suite of
“orthopyroxene” (Enstitite-Ferrosilite).
Inosilicate Minerals (clinopyroxenes)
There are more options for
ternary plots as there is more
variability in cation composition
Clinopyroxenes
… and you are going to ♥ the
phase diagram possibilities
Inosilicate Minerals (clinopyroxenes)
… and you are going to ♥ the
phase diagram possibilities
Pressure-Temperature relations
of Enstatite (MgSiO3)
http://www.uni-muenster.de/
Inosilicate Minerals (clinopyroxenes)
… and you are going to ♥ the
phase diagram possibilities
Augite-Pigeonite phase
diagram
http://www.uni-muenster.de/
Inosilicate Minerals (clinopyroxenes)
… and you are going to ♥ the
phase diagram possibilities
Pyroxene behavior subject to
burial in the mantle….
….etc.
http://serc.carleton.edu/NAGTWorkshops/
Today’s Agenda
Class VIII Minerals: Inosilicates (part 2)
1.
Amphiboles
Inosilicates (double chain)
Two major sub groups of amphiboles are distinguished on the
basis of crystal structure:
1) Orthorhombic Amphiboles
2) Monoclinic Amphiboles
http://www.uwgb.edu/dutchs/GRAPHIC0/ROCKMIN/ATOM-STRUCT/amphibchain.gif
Inosilicates (double chain)
General formula: XY((Al,Si)4O11)2(OH)2
X[larger ions] = Ca2+, Na+
Y[smaller ions] = Mg2+, Al3+, Fe2+/3+, Mn2+/3+)
http://www.tulane.edu/~sanelson/images/amphibole_cleavage.gif
Inosilicates (single chain)
Inosilicates (double chain)
Mineral
Formula
System
(Mg,Fe)7Si8O22(OH)2
Orthorhombic
Orthorhombic Amphiboles
Anthophyllite-Gedrite
Monoclinic Amphiboles
Cummingtonite
Grunerite
Tremolite
Actinolite
Hornblende
Glaucophane
Riebekite
(Mg)7Si8O22(OH)2
(Fe2+)7Si8O22(OH)2
Ca2Mg5Si8O22(OH)2
Ca2(Mg,Fe2+)5Si8O22(OH)2
(Ca,Na,K)2-3(Mg,Fe,Al)5Si6(Si,Al)2O22(OH,F)2
Na2Mg3Al2Si8O22(OH)2
Na2Fe2+3Fe3+2Si8O22(OH)2
Monoclinic
Monoclinic
Monoclinic
Monoclinic
Monoclinic
Monoclinic
Monoclinic
http://www.geol.lsu.edu/henry/Geology7900/Amphibole/images/
Inosilicates (double chain)
Inosilicates (double chain)
http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif
Inosilicates (double chain)
We recognize several amphibole series (solid
solution)
1) Anthophyllite Series (Orthorhombic)
http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif
Anthophyllite
Gedrite
(Mg,Fe2+)7Si8O22(OH)2
(Mg,Fe2+)5Al2(Si6Al2O22)(OH,F)2
Inosilicates (double chain)
We recognize several amphibole series (solid
solution)
1) Anthophyllite Series (Orthorhombic)
2) Cummingtonite Series (Monoclinic)
http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif
Cummingtonite
(Mg,Fe2+)7Si8O22(OH)2
30 to 70% Fe
Grunerite
(Fe2+,Mg)7(Si8O22)(OH)2
>70% Fe
Inosilicates (double chain)
We recognize several amphibole series (solid
solution)
1) Anthophyllite Series (Orthorhombic)
2) Cummingtonite Series (Monoclinic)
3) Actinolite Series (Monoclinic)
http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif
Tremolite
Ca2Mg5Si8O22(OH)2
Actinolite
Ca2(Fe2+,Mg)5Si8O22(OH)2
Ferroactinolite
Ca2(Fe2+)5Si8O22(OH)2
Inosilicates (double chain)
We recognize several amphibole series (solid
solution)
1) Anthophyllite Series (Orthorhombic)
2) Cummingtonite Series (Monoclinic)
3) Actinolite Series (Monoclinic)
4) Hornblende Series (Monoclinic)
5) Glaucophane Series (Monoclinic)
6) Riebeckite Series (Monoclinic)
7) Arfvedsonite-Eckermannite Series (Mono)
http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif
“Hornblende”: (Ca,Na,K)2-3(Mg,Fe,Al)5Si6(Si,Al)2O22(OH)2
“Glaucophane”: Na2Mg3Al2Si8O22(OH)2
“Riebeckite”: Na2Fe2+3Fe3+2Si8O22(OH)2
“Arvedsonite”: Na3(Mg,Fe2+)4AlSi8O22(OH)2
Inosilicate Minerals (Orthorhombic Amphiboles)
Anthophyllite
[(Mg,Fe)7Si8O22(OH)2 ]
Crystal: Orthorhombic
Pt. Group: 2/m 2/m 2/m
Habit: Fibrous, massive
SG: 3.21; H: 5-6
L: silky to pearly; Str: grey
Col: white, greyish, brownish, brown-green
Clev: perfect [110]
Optics: Biaxial (+); bir=0.070-0.023
nα=1.598; nβ=1.605, nγ=1.615
Occurrence: Metamorphic rocks
From the Latin anthophyllum - "clove" in allusion to the color.
Asbestos Minerals
Several minerals with a fibrous habit that have useful economic
properties (flexible, high melting points, tensile strength, heat resistance)
Amphibole Asbestos minerals: Anthophyllite, Tremolite, Amosite, Actinolite, Crocidolite
Serpentine Asbestos minerals: Clinochrysotile, Orthochrysotile
http://z.about.com/d/geology/1/0/7/z/chrysotilecloseup.jpg
Asbestos Minerals
Several minerals with a fibrous habit that have useful economic
properties (flexible, high melting points, tensile strength, heat resistance)
Amphibole Asbestos minerals: Anthophyllite, Tremolite, Amosite, Actinolite, Crocidolite
Serpentine Asbestos minerals: Clinochrysotile, Orthochrysotile
Crocidolite (“blue
asbestos”) is part
of the Riebeckite
series and is the
worst of the
asbestos minerals
(at least according
to legal websites)
http://www.earthsci.unimelb.edu.au/Thomas/lteng/engeimg/enge0247a.JPG
Inosilicate Minerals (Monoclinic Amphiboles)
Cummingtonite
[Mg7Si8O22(OH)2]
Crystal: Monoclinic
Pt. Group: 2/m
Habit: fibrous, massive, columnar
SG: 3.35; H: 5-6
L: silky; Str: grey-white
Col: white, brown, black, grey
Clev: perfect [110]
Optics: Biaxial (+); bir=0.025-0.037
nα=1.639; nβ=1.647, nγ=1.664
Occurrence: metamorphic rocks
http://webmineral.com
Named after its locality Cummington, Massachusetts, USA.
Inosilicate Minerals (Monoclinic Amphiboles)
Hornblende
(Ca,Na,K)2-3(Mg,Fe,Al)5Si6(Si,Al)2O22(OH,F)2
Crystal: Monoclinic
Pt. Group: 2/m
Habit: prismatic (short stocky)
SG: 3.0-3.47; H: 5-6
L: vitreous to pearly; Str: white
Col: brown, green, dark green
Clev: perfect {001}
Optics: Biaxial (-); bir=0.020
nα=1.616; nβ=1.626, nγ=1.636
Occurrence: Metamorphic/Intermediate
Igneous rocks
Not so much a mineral as a suite of minerals
(data here is for Magnesiohornblende)
Inosilicate Minerals (Monoclinic Amphiboles)
Riebeckite
[Na2Fe2+Fe3+Si8O22(OH)2]
Crystal: Monoclinic
Pt. Group: 2/m
Habit: massive, fibrous
SG: 3.07; H: 6 to 6.5
L: vitreous-pearly; Str: greenish-brown
Col: blue, black, dark green
Clev: [110] perfect
Optics: Biaxial (-); bir=0.005-0.008
nα=1.68; nβ=1.683, nγ=1.685
Occurrence: Igneous &
Metamorphic rocks
http://webmineral.com
Named after a German “traveler”; Eril Riebeck (1853-1885)
Inosilicate Minerals (Monoclinic Amphiboles)
Glaucophane
[Na2Mg3Al2Si8O22(OH)2]
Crystal: Monoclinic
Pt. Group: 2/m
Habit: massive, fibrous
SG: 3.07; H: 6 to 6.5
L: vitreous-pearly; Str: grey-blue
Col: blue, grey-blue, lavender blue
Clev: Good [110], [001]
Optics: Biaxial (-); bir=0.018-0.021
nα=1.606; nβ=1.615, nγ=1.627
Occurrence: Blue schist (meta)
http://webmineral.com/specimens/picshow.php?id=1840
From the Greek glaukos - "blue" and fanos - "appearing."
Today’s Stuff To Do
1.
Work on your posters!
Today’s Lab
1.
Quiz 8 (Neso/Soro/Cyclosilicates 1:00 -1:30 PM)
On Line Lecture
1.
Lecture 23 (Phyllosilicates 1: micas)
Thursday
1.
Discussion; rock forming mineral identification…in rocks!
GY 302: Crystallography and
Mineralogy
Lecture 22: Silicates 5: Amphiboles
Instructor: Dr. Doug Haywick
dhaywick@southalabama.edu
This is a free open access lecture, but not for commercial purposes.
For personal use only.