Augite
Image: Shannon Heinle (CC0)
Mineral NameAugite
Chemical Formula(Ca,Na)(Mg,Fe,Al)(Al,Si)2O6
Mohs Hardness6
Crystal Systemmonoclinic
Lustervitreous
Streak Colorwhite to grayish-green
CleavageTwo distinct cleavages at nearly 90 degrees (87 and 93 degrees)
Fractureuneven to conchoidal
Specific Gravity3.4
Colorsdark green, black, brownish-black
Transparencyopaque to translucent
Type LocalityEganville, Ontario, Canada
Mineral GroupSilicates (Pyroxene Group)
Usesrock-forming mineral, collector specimens
Associated Mineralsplagioclase, olivine, magnetite, hornblende
Raritycommon
Description
This sample shows a dark, blocky, prismatic crystal of augite, approximately 4.5 cm across, with a somewhat dull to vitreous luster typical of the mineral.
Geological Context
Augite is a common and important rock-forming mineral found in many mafic and ultramafic igneous rocks such as gabbro and basalt, as well as in some high-grade metamorphic rocks like amphibolites and granulites.
