Days 22


These pages are under construction, and contian class notes....

INOSILICATES

Pyroxenes
Single-chain inosilicates with Si:O ratio of 1:3 Pyroxenes are major rock forming minerals of earth's crust and mantle, also of lunar rocks.

Si:O in chain in 1:3 ratio, orthopyroxenes are XSiO3 and clinopyroxenes are XYSi2O6 - major component of igneous rocks, classifications of many plutonic rocks are based on pyroxenes - appearance of pyroxene in most metamorphic rocks is part of the granulite facies - sodic pyroxenes (jadeite, omphacite) are indicative of high pressure

Orthopyroxenes
Enstatite MgSiO3 Orthorhombic
Ferrosilite FeSiO3 Orthorhombic
*Bronzite (En70-90) and hypersthene, (En50-70) are common names for solid-solutions in the enstatite-ferrosilite series.

Clinopyroxenes
Diopside CaMgSi2O6 Monoclinic
Hedenbergite CaFeSi2O6 Monoclinic
Augite (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6 Monoclinic
Pigeonite Ca0.25(Mg,Fe) 1.75Si2O6 Monoclinic
Aegirine NaFeSi2O6 Monoclinic
Jadeite NaAlSi2O6 Monoclinic
*Omphacite is a high-pressure solid solution between augite and jadeite.

Pyroxenoids
Wollastonite CaSiO3 Triclinic

Amphiboles
Double-chain inosilicates with a Si:O ratio of 4:11, and (OH)

Orthorhombic Amphiboles
Anthophyllite-Gedrite (Mg,Fe) 7Si8O22(OH)2 Orthorhombic

Monoclinic Amphiboles (Clino-amphiboles)
Cummingtonite-Grunerite (Fe,Mg) 7Si8O22(OH)2 Monoclinic
Tremolite-Actinolite Ca2(Mg,Fe) 5Si8O22(OH)2 Monoclinic
Hornblende (Ca,Na,K)2-3(Mg,Fe,Al)5Si6(Si,Al)2O22(OH)2 Monoclinic
Glaucophane Na2Mg3Al2Si8O22(OH)2 Monoclinic
Riebekite Na2Fe3Fe2Si8O22(OH)2 Monoclinic

Mineral Formula Calculation - Examples of Ortho- and Clinopyroxenes

Wt. % Oxides Molec. Wt. Oxides Molecular Porp. Atomic Prop. Sum Molec Prop. = MPF

Calculation of Mineral Formulas for Hydrous Minerals.

Plotting of compositions (wt %, Molecular %, atomic %) in triangular diagrams - extent of solid solution - coexistence of minerals in a specific rock type


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