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+ Si:O ratio is 1:3 (larger cations force triclinic symmetry) http://ruby.colorado.edu 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) Enstitite is actually one member of a continuous series suite of “orthopyroxene” (Enstitite-Ferrosilite). Textbook’s “mineral” (p265) Orthopyroxenes hyperstene http://ruby.colorado.edu/~smyth/min/images/enstatite.gif http://upload.wikimedia.org/wikipedia/en/4/42/Pyrox_names.png 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 2+ + X[larger ions] = Ca , Na 2+ 3+ 2+/3+ 2+/3+ Y[smaller ions] = Mg , Al , Fe , Mn ) 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 2+ Grunerite (Fe )7Si8O22(OH)2 Monoclinic Tremolite Ca2Mg5Si8O22(OH)2 Monoclinic 2+ Actinolite Ca2(Mg,Fe )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 2+ 3+ Riebekite Na2Fe 3Fe 2Si8O22(OH)2 Monoclinic Inosilicates (double chain) http://www.geol.lsu.edu/henry/Geology7900/Amphibole/images/ 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 2+ 2+ (Mg,Fe )7Si8O22(OH)2 (Mg,Fe )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 Grunerite 2+ 2+ (Mg,Fe )7Si8O22(OH)2 (Fe ,Mg)7(Si8O22)(OH)2 30 to 70% Fe >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 Actinolite Ferroactinolite 2+ 2+ Ca2Mg5Si8O22(OH)2 Ca2(Fe ,Mg)5Si8O22(OH)2 Ca2(Fe )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 2+ 3+ “Riebeckite”: Na2Fe 3Fe 2Si8O22(OH)2 2+ “Arvedsonite”: Na3(Mg,Fe )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 http://webmineral.com nα=1.639; nβ=1.647, nγ=1.664 Occurrence: metamorphic rocks 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} Not so much a mineral as a suite of minerals Optics: Biaxial (-); bir=0.020 (data here is for Magnesiohornblende) nα=1.616; nβ=1.626, nγ=1.636 Occurrence: Metamorphic/Intermediate Igneous rocks Inosilicate Minerals (Monoclinic Amphiboles) Riebeckite 2+ 3+ [Na2Fe Fe 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 http://webmineral.com nα=1.68; nβ=1.683, nγ=1.685 Occurrence: Igneous & Metamorphic rocks 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 http://webmineral.com/specimens/picshow.php?id=1840 nα=1.606; nβ=1.615, nγ=1.627 Occurrence: Blue schist (meta) 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 12:15 -12:45 PM) On Line Lecture 1. Nothing this week (syllabus change) Thursday 1. Lecture 23 (Phyllosilicates 1: micas) 2. Discussion; rock forming mineral identification…in rocks! GY 302: Crystallography and Mineralogy Lecture 22: Silicates 5: Amphiboles Instructor: Dr. Doug Haywick [email protected] This is a free open access lecture, but not for commercial purposes. For personal use only. .