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302-pp21 - Quiz 8 results 1 Wulfenite(79 2 Purpurite(79 3...

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Quiz 8 results 1: 1: Wulfenite (79% Wulfenite (79% ) ) 2: 2: Purpurite Purpurite (79% (79% ) ) 3. 3. Varascite Varascite (79% (79% ) ) 4: 4: Wolframite Wolframite (74% (74% ) ) 5: 5: Barite (53% Barite (53% ) ) 6: 6: Celestine (68% Celestine (68% ) ) Bonus: Bonus: Gibsite Gibsite (32% (32% ) ) Average: 82.6% Highest grade: 108% A: 7 B: 5 C: 3 D: 2 F: 2
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GY 302: Crystallography & Mineralogy GY 302: Crystallography & Mineralogy UNIVERSITY OF SOUTH ALABAMA Lecture 21: Inosilicates 1 Pyroxenes and Pyroxenoids Lecture 21: Inosilicates 1 Pyroxenes and Pyroxenoids
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Class VIII Minerals 1. Sorosilicates 2. Cyclosilicates (3, 4 and 6 fold coordination) Last Time
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Sorosilicates Mineral Formula System Zoisite Ca 2 Al 3 O(SiO 4 )(Si 2 O 7 )(OH) Orthorhombic Clinozoisite Ca 2 Al 3 O(SiO 4 )(Si 2 O 7 )(OH) Monoclinic Epidote Ca 2 (Al,Fe)Al 2 O(SiO 4 )(Si 2 O 7 )(OH) Monoclinic Allanite (Ca,Ce) 2 (Fe,Fe)Al 2 O(SiO 4 )(Si 2 O 7 )(OH) Monoclinic Lawsonite CaAl 2 SiO 7 (OH) 2 ·H 2 O Orthorhombic Pumpellyite Ca 2 MgAl 2 (SiO 4 )(Si 2 O 7 )(OH)2·H 2 O Monoclinic Vesuvianite (Idocrase) Ca 10 Mg 2 Al 4 (SiO 4 ) 5 (Si 2 O 7 ) 2 (OH) 4 Tetragonal Hemimorphite Zn 4 Si 2 O 7 (OH) 2 ·(H 2 O) Orthorhombic
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Hemimorphite [Zn 4 Si 2 O 7 (OH) 2 ·H 2 O] Crystal: Orthorhombic Pt. Group: 2mm Habit: massive to mammillary SG: 3.45; H: 5 L: vitreous; Str: white Col: colorless, brown, to grey Clev: perfect [001] Optics: Biaxial (+); bir=0.020 n α =1.61; n β =1.62, n γ =1.736 Sorosilicate Minerals http://webmineral.com/data/Hemimorphite.shtml Named after the hemimorphic nature of the crystals.
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Cyclosilicates Mineral Formula System Beryl Be 3 Al 2 Si 6 O 18 Hexagonal “Tourmaline” (Na,Ca)(Li,Mg,Al)(Al,Fe,Mn) 6 (BO 3 ) 3 (Si 6 O 18 )(OH) 4 Hexagonal (Trigonal) Cordierite Al 3 (Mg, Fe) 2 (AlSi 5 O 18 ) Orthorhombic Axinite (Ca, Mn, Fe) 3 Al 2 (BO 3 )Si 4 O 12 (OH) Triclinic Dioptase CuSiO 2 (OH) 2 Hexagonal (Trigonal) Silicate rings come in 3, 4 and 6 fold structures. 8-fold structures also occur in nature (e.g., sulfur)
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Cyclosilicate Minerals 6 fold ring structure
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Beryl [Be 3 Al 2 Si 6 O 18 ] Crystal: Hexagonal Pt. Group: 6/m 2/m 2/m Habit: euhedral, columnar SG: 2.76; H: 7.5-8 L: vitreous; Str: white Col: blue, yellow, red, green Clev: imperfect Optics: Uniaxial (-); bir=0.004-0.007 n e =1.564; n w =1.568 Cyclosilicate Minerals (6-fold rings) http://webmineral.com/specimens/picshow.php?id=123 From the ancient Greek, beryllos, signifying a "precious blue-green color of sea water" stone.
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