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GY 302: Crystallography & Mineralogy

UNIVERSITY OF SOUTH ALABAMA

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+

Si:O ratio is 1:3

(octahedrally coordinated cations between SiO3 chains

produce orthorhombic or monoclinic symmetries)

http://ruby.colorado.edu

Monoclinic Orthorhombic

Inosilicates (pyroxenoids)

General formula: X2SiO3

X[larger ions] = Ca2+, Na+, Fe2+ and/or Mg2+

Si:O ratio is 1:3 (larger cations force triclinic

symmetry)

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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

Enstitite is actually one member of a continuous series suite of “orthopyroxene” (Enstitite-Ferrosilite).

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Inosilicate Minerals (orthopyroxene)

http://upload.wikimedia.org/wikipedia/en/4/42/Pyrox_names.png

Textbook’s “mineral” (p265)

hyperstene

Orthopyroxenes

Inosilicate Minerals (clinopyroxenes)

Clinopyroxenes

There are more options for ternary plots as there is more variability in cation composition

… 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 Orthorhombic Amphiboles Anthophyllite-Gedrite (Mg,Fe)7Si8O22(OH)2 Orthorhombic Monoclinic Amphiboles Cummingtonite (Mg)7Si8O22(OH)2 Monoclinic Grunerite (Fe2+)7Si8O22(OH)2 Monoclinic Tremolite Ca2Mg5Si8O22(OH)2 Monoclinic Actinolite Ca2(Mg,Fe2+)5Si8O22(OH)2 Monoclinic Hornblende (Ca,Na,K)2-3(Mg,Fe,Al)5Si6(Si,Al)2O22(OH,F)2 Monoclinic Glaucophane Na2Mg3Al2Si8O22(OH)2 Monoclinic Riebekite Na2Fe2+

3Fe3+2Si8O22(OH)2 Monoclinic

Inosilicates (double chain)

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Inosilicates (double chain)

http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif

Inosilicates (double chain)

http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif

We recognize several amphibole series (solid solution) 1) Anthophyllite Series (Orthorhombic)

Anthophyllite Gedrite

(Mg,Fe2+)7Si8O22(OH)2 (Mg,Fe2+)5Al2(Si6Al2O22)(OH,F)2

Inosilicates (double chain)

http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif

We recognize several amphibole series (solid solution) 1) Anthophyllite Series (Orthorhombic) 2) Cummingtonite Series (Monoclinic)

Cummingtonite Grunerite

(Mg,Fe2+)7Si8O22(OH)2 (Fe2+,Mg)7(Si8O22)(OH)2

30 to 70% Fe >70% Fe

Inosilicates (double chain)

http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif

We recognize several amphibole series (solid solution) 1) Anthophyllite Series (Orthorhombic) 2) Cummingtonite Series (Monoclinic) 3) Actinolite Series (Monoclinic)

Tremolite Actinolite Ferroactinolite Ca2Mg5Si8O22(OH)2 Ca2(Fe2+,Mg)5Si8O22(OH)2 Ca2(Fe2+)5Si8O22(OH)2

Inosilicates (double chain)

http://www.tulane.edu/~sanelson/images/amphibole-compositions.gif

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) “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

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

Inosilicate Minerals (Orthorhombic Amphiboles)

From the Latin anthophyllum - "clove" in allusion to the color.

Several minerals with a fibrous habit that have useful economic properties (flexible, high melting points, tensile strength, heat resistance)

Asbestos Minerals

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

Several minerals with a fibrous habit that have useful economic properties (flexible, high melting points, tensile strength, heat resistance)

Asbestos Minerals

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

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

Named after its locality Cummington, Massachusetts, USA.

Inosilicate Minerals (Monoclinic Amphiboles)

http://webmineral.com

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

Inosilicate Minerals (Monoclinic Amphiboles)

Not so much a mineral as a suite of minerals (data here is for Magnesiohornblende)

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

Inosilicate Minerals (Monoclinic Amphiboles)

http://webmineral.com

Named after a German “traveler”; Eril Riebeck (1853-1885)

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)

Inosilicate Minerals (Monoclinic Amphiboles)

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!

Thursday 1. Lecture 23 (Phyllosilicates 1: micas)

2. Discussion; rock forming mineral identification…in rocks!

Today’s Lab 1. Quiz 8 (Neso/Soro/Cyclosilicates 12:15 -12:45 PM)

On Line Lecture 1. Nothing this week (syllabus change)

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.