Augite (var. Fassaite)
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 4.0)
Mineral NameAugite (var. Fassaite)
Chemical Formula(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)2O6
Mohs Hardness5.5
Crystal Systemmonoclinic
Streak Colorwhite to grayish-green
CleavageTwo distinct cleavages at nearly 90 degrees (87 and 93 degrees)
Fractureuneven to conchoidal
Specific Gravity3.2
Colorsdark green, black, brownish-green
Transparencyopaque to translucent
Type LocalityToal de la Foia, Monti Monzoni, Val di Fassa, Trento, Trentino-Alto Adige, Italia
Mineral GroupSilicates (Inosilicates, Pyroxene Group)
Usescollector's mineral, petrological studies
Associated Mineralsplagioclase, olivine, hornblende, garnet
Rarityuncommon
Description
This specimen features dark green to black, prismatic crystals of Fassaite embedded in a lighter, granular matrix. The crystals exhibit a vitreous to sub-metallic luster.
Geological Context
Fassaite, a variety of augite, typically forms in contact metamorphic skarns and calc-silicate rocks, often associated with alkaline igneous intrusions. It is characteristic of high-temperature, low-pressure metamorphic environments.
