Mineral Quizzes Results - University of South Alabama
Transcript of Mineral Quizzes Results - University of South Alabama
GY 302: Crystallography & Mineralogy
UNIVERSITY OF SOUTH ALABAMA
Lecture 23: Phyllosilicates 1
Mica Minerals etc.
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 (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
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
Today’s Agenda
Phyllosilicates Part 1 1. General chemistry/structure 2. Phyllosilicate classification
3. Mica, chlorite and talc groups
Phyllosilicates Si:O ratio = 2:5 (3 shared oxygens)
Anion component: Si4O10
-4 or Si8O20-8
With Al substitution: AlSi3O10
-5 or Al2Si2O10-6
Phyllosilicates Si:O ratio = 2:5 (3 shared oxygens)
Anion component: Si4O10
-4 or Si8O20-8
With Al substitution: AlSi3O10
-5 or Al2Si2O10-6
General Formula: XYAlSi3O10(OH)2
X = K+, Na+, Li+, Ca2+ Y = Fe2+/3+, Mg2+, Al3+, rarely Cr3+, Ni3+, Mn3+
Example (Muscovite): KAl2 AlSi3O10(OH)2
Phyllosilicate Structure Inosilicate Structure
(Amphibole)
Si4O116-
Phyllosilicate Structure (Mica)
Si4O104-
Phyllosilicate Structure Tetrahedral layers
(mostly SiO44-)
Octahedral layers (variable; Al/Mg/OH)
Cation layers (K+, Mg2+, Na+ etc.)
also H2O (clays)
Phyllosilicate Structure The octahedral layers are given specific names according to the nature of the “filling”. Need 6 x OH for octahedral coordination
Phyllosilicate Structure The octahedral layers are given specific names according to the nature of the “filling”. Need 6 x OH for octahedral coordination Al2(OH)6 = Gibbsite Layer (Al(OH)3) 2 x Al = dioctahedral coordination Mg3(OH)6 = Brucite Layer (Mg(OH)2) 3 x Mg = trioctahedral coordination
Phyllosilicate Classification Is rather nasty, but most are either monoclinic or triclinic. Classification is further done of the basis of:
Phyllosilicate Classification Is rather nasty, but most are either monoclinic or triclinic. Classification is further done of the basis of: 1. Composition of octahedral layer
Phyllosilicate Classification Is rather nasty, but most are either monoclinic or triclinic. Classification is further done of the basis of: 1. Composition of octahedral layer 2. Repeat distance (distance between T-O-T “sandwiches”)
Phyllosilicate Classification Is rather nasty, but most are either monoclinic or triclinic. Classification is further done of the basis of: 1. Composition of octahedral layer 2. Repeat distance (distance between T-O-T “sandwiches”) 3. Whether structure is expandable (clays)
Phyllosilicate Classification Is rather nasty, but most are either monoclinic or triclinic. Classification is further done of the basis of: 1. Composition of octahedral layer 2. Repeat distance (distance between T-O-T “sandwiches”) 3. Whether structure is expandable (clays) 4. Number of layers in the “sandwiches” (2 versus 3)
Phyllosilicate Classification
1:1 Structure (kaolinite, serpentine, halloysite,
Chrysotile, allophane)
2:1 Structure (Most micas and clays)
Phyllosilicate Classification
1:1 Structure (kaolinite, serpentine, halloysite,
Chrysotile, allophane)
2:1 Structure (Most micas and clays)
1:1 & 2:1 Interlayered (Chlorite Group)
Biotite [K(Fe,Mg)3AlSi3O10(OH)2 ]
Crystal: Monoclinic Pt. Group: 2/m Habit: platy (flexible) SG: 2.8-3.4; H: 2.5-3 L: vitreous to pearly; Str: grey Col: brown (reddish to greenish) Clev: perfect [001] Optics: Biaxial (-); bir=0.030-0.070 nα=1.522; nβ=1.548, nγ=1.549 Occurrence: Intermediate Ig; med. grade metamorphic rocks Named after French physicist, Jean Baptiste Biot (1774 -
1862), who studied the optical properties of the micas.
Phyllosilicate Minerals (micas, 2:1 layers)
Phyllosilicate Minerals (micas, 2:1 layers)
From Muscovy glass, alluding to the Russian province of Muscovy. Occurrence: pegmatitic Ig., med
grade Meta, sericite in Sed. rocks
Muscovite [KAl2 AlSi3O10(OH)2]
Crystal: Monoclinic Pt. Group: 2/m Habit: platy (flexible) SG: 2.82; H: 2 to 2.5 L: vitreous to pearly; Str: white Col: white (gold, silver, green) Clev: Perfect [001] Optics: Biaxial (-); bir=0.036-0.049 nα=1.552; nβ=1.582, nγ=1.587
Fuchsite (v. muscovite)
[K(Al,Cr)2 AlSi3O10(OH)2] Crystal: Monoclinic Pt. Group: 2/m Habit: platy (flexible) SG: 2.82; H: 2 to 2.5 L: vitreous to pearly; Str: white Col: emerald green Clev: Perfect [001] Optics: Biaxial (-); bir=0.032 nα=1.569; nβ=1.598, nγ=1.601
The Cr-variety of muscovite. The Ba-rich variety is called Binnite
http://www.dakotamatrix.com/images/products/fuchsite15805a.jpg
Phyllosilicate Minerals (micas, 2:1 layers)
Occurrence: metamorphic rocks
Phlogopite (biotiote series)
[KMg3AlSi3O10(OH)2 ] Crystal: Monoclinic Pt. Group: 2/m Habit: platy SG: 2.8; H: 2 to 2.5 L: vitreous to pearly; Str: white Col: brown, green, reddish-brown Clev: perfect [001] Optics: Biaxial (-); bir=0.028-0.045 nα=1.53; nβ=1.557, nγ=1.558
Name Derivation: From the Greek flogopos - "resembling fire."
http://cache.eb.com/eb/image?id=9648&rendTypeId=4
Phyllosilicate Minerals (micas, 2:1 layers)
Occurrence: Ultramafic Ig; Meta carbonates
Lepidolite (biotite series)
[K(Li,Al)2-3AlSi3O10(OH)2 ] Crystal: Monoclinic Pt. Group: 2/m Habit: platy SG: 2.84; H: 2.5-3 L: vitreous to pearly; Str: white Col: lilac (yellowish) to colourless Clev: perfect [001] Optics: Biaxial (-); bir=0.029-0.038 nα=1.525; nβ=1.551, nγ=1.554
Name Derivation: From the Greek lepidion - "scale"
http://webmineral.com/specimens/picshow.php?id=671
Phyllosilicate Minerals (micas, 2:1 layers)
Occurrence: Li-bearing pegmatites
Margarite [CaAl2Al2Si2O10(OH)2 ]
Crystal: Monoclinic Pt. Group: 2/m Habit: scaly, massive SG: 3.03; H: 4 L: pearly; Str: white Col: white, grey (pinkish) Clev: good [001] Optics: Biaxial (-); bir=0.012-0.032 nα=1.595; nβ=1.625, nγ=1.627
From the Greek margaritos - "pearl."
http://webmineral.com/specimens/picshow.php?id=671
Phyllosilicate Minerals (micas, 2:1 layers)
Occurrence: alteration product associated with corundum
Clinochlore (Chlorite Group) (Mg,Fe)3(Al,Si)4O10(OH)2(Mg,Fe)3(OH)6
Crystal: Monoclinic Pt. Group: 2/m Habit: scaly, massive SG: 2.65; H: 2 to 2.5 L: vitreous to pearly; Str: white Col: green to black Clev: perfect [001] Optics: Biaxial (+); bir=0.005-0.011 nα=1.571; nβ=1.571; nγ=1.576
From the Greek klino - "oblique" and chloros - " green.
Phyllosilicate Minerals (interlayered)
http://itc.gsw.edu/faculty/tweiland/chlorit.jpg
Occurrence: Low grade metamorphosed mafic rocks, burial-grade sedimentary diagenesis
Talc (Talc Group) [Mg3Si4O10(OH)2]
Crystal: Monoclinic Pt. Group: 2/m Habit: scaly, massive SG: 2.75; H: 1 L: vitreous to pearly; Str: white Col: any colour, including smurf Clev: perfect [001] Optics: Biaxial (-); bir=0.037-0.050 nα=1.538; nβ=1.575, nγ=1.575
From the Arabian “talcia” meaning keep baby’s ass dry
Phyllosilicate Minerals (2:1 layers)
http://www.soes.soton.ac.uk/resources/collection/minerals/minerals
Occurrence: hydrothermal metamorphism
Pyrophyllite Al2Si4O10(OH)2
Crystal: Triclinic Pt. Group: 1 Habit: massive, acicular SG: 2.75; H: 1.5 to 2 L: pearly; Str: white Col: brown, grey, green, white Clev: perfect [001] Optics: Biaxial (-); bir=0.045-0.062 nα=1.534; nβ=1.586, nγ=1.596
Phyllosilicate Minerals (talc group; 2:1 layers)
http://www.mindat.org/photo-60228.html
Occurrence: hydrothermal metamorphic veins
From the Greek pyr - "fire" and phyllon – “leaf”
GY 302: Crystallography and Mineralogy
Lecture 23: Silicates 6: Micas
Instructor: Dr. Doug Haywick [email protected]
This is a free open access lecture, but not for commercial purposes.
For personal use only.