THE PYROXENE GROUP OF MINERALS

THE PYROXENE GROUP OF MINERALS [...]... silicates or more precisely between pyroxene minerals and amphibole minerals  The amphiboles contain the same elements that the pyroxenes do, except they have hydroxyl (OH) in their structure, which alters both its physical and chemical properties  For example: Augite- (Ca,Mg,Fe)SiO3  Hornblende- Ca2(Mg, Fe, Al)5 (Al, Si)8O22(OH)2 Clino pyroxene group Clino pyroxene (Diopside series) Diopside Ca... This difference produces a difference in angles  The cleavage of the two groups results between chains and does not break the chains thus producing prismatic cleavage  In the single chained silicates the two directions of cleavage are at 87° and 93° (close to 90 degrees) forming nearly square cross sections  In the double chain silicates the cleavage angles are at 56° and 124° (close to 120... especially Na  Omphacite is a bright green variety of augite rich in Na and Al Jadeite  The term jade refers to either jadeite or to the amphibole, nephrite  It is a high pressure pyroxene found in metamorphic rocks of the blueschist facies  Associated with glaucophane, lawsonite or aragonite, and with quartz and epidote  A bright green variety of jadeite, omphacite, occurs in eclogites with pyrope... clino pyroxene end members diopside and heldenbergite Enstatite- Ferrosilite Enstatite Bronzite Hypersthene Ferrohypersthene Eulite Orthoferrosilite 0-10(% Fe) 10-30 30-50 50-70 70-90 90-100 Occurrence and associations  Enstatite is more common in mafic igneous rocks  Commonly associating with plagioclase and clinopyroxene  Also in high- grade metamorphic rocks and is considered diagnostic for the. .. and is considered diagnostic for the granulite facies  Hypersthene is a characteristic mineral associated with charnockite series of rocks  Eulite and Orthoferrosilite- associated with fayalite, hedenbergite, grunerite and almandine – spessartine garnet, of eulysite, a regionally metamorphosed Iron rich sediment Augite  Most common pyroxene found in mafic to intermediate igneous rocks, both plutonic... Ca Fe Si2 O6 Pyroxene Solid solutions Pigeonite (Ca, Mg, Fe)2 Si2 O6 Augite (Ca, Mg, Fe, Na) (Mg, Fe, Al) (Si, Al)2 O6 Omphacite (Ca, Na )(Fe Mg Al) (Si, Al)2 O6 Aegirine Na (Al, Fe3+) Si2 O6 Na and Li pyroxenes Jadeite Na Al Si2 O6 Spodumene Li Al Si2 O6 General formula (w,x,y)2 Z2 O6  In which w, x, y, z indicate elements having similar ionic radii and capable of replacing each otherin the structure... Diopside is the most common pyroxene Found in mafic and ultramafic igneous rocks Found in marbles associated with calcite, quartz or forsterite, tremolite and garnet Also found in medium and high grade metamorphosed mafic rocks Hedenbergite is often found associated with ore deposits formed at high temperatures AUGITE AEGIRINE DIOPSIDE Enstatite- Ferrosilite Enstatite Mg Si O3 Ferrosilite FeSiO3 Hypersthene&... tourmaline, beryl and lepidolite  Hiddenite is a name given to emerald green spodumene  Kunzite to lilac/pink colour spodumene  Triphane to colourless or yellow spodumene ENSTATITE FERROSILITE HYPERSTHENE THE END . THE PYROXENE GROUP OF MINERALS