Augite

Big Photo

New Mexico, USA
2.87 carats
© Rarestone.com

Augite is named from Greek "auge" - bright, referring to the appearance of its cleavage planes.

Augite forms glassy crystals ranging in colour from purple and brown to black. Large lustrous crystals are not uncommon.

Augite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
General Information
Chemical Formula
(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)
 
2
O
 
6
Anthony et al, Handbook of mineralogy (2001)
Photos of natural/un-cut material from mindat.org
Physical Properties of Augite
Mohs Hardness5.5 to 6
Anthony et al, Handbook of mineralogy (2001)
Specific Gravity3.19 to 3.56
Anthony et al, Handbook of mineralogy (2001)
TenacityBrittle
Anthony et al, Handbook of mineralogy (2001)
Cleavage QualityGood
Anthony et al, Handbook of mineralogy (2001)
FractureUneven,Conchoidal
Anthony et al, Handbook of mineralogy (2001)
Optical Properties of Augite
Refractive Index1.671 to 1.774
Anthony et al, Handbook of mineralogy (2001)
Optical CharacterBiaxial/+
Anthony et al, Handbook of mineralogy (2001)
PleochroismPale green, pale brown, green, greenish yellow - pale brown, pale yellow-green, violet - pale green, grayish green, violet.
Anthony et al, Handbook of mineralogy (2001)
DispersionWeak to moderate
Anthony et al, Handbook of mineralogy (2001)
Colour
Colour (General)Black, brown, greenish, violet-brown; in thin section, colorless to gray; clear cores zoned to dark rims common, also oscillatory and sector zoning.
Anthony et al, Handbook of mineralogy (2001)
TransparencyTransparent,Translucent,Opaque
Anthony et al, Handbook of mineralogy (2001)
LustreVitreous,Resinous,Dull (Earthy)
Anthony et al, Handbook of mineralogy (2001)
Crystallography of Augite
Crystal SystemMonoclinic
Anthony et al, Handbook of mineralogy (2001)
HabitStubby prismatic crystals, square or octagonal in section, to 10 cm; elongated, acicular, skeletal, dendritic. Exsolution lamellae and overgrowths common
Anthony et al, Handbook of mineralogy (2001)
Geological Environment
Where found:Essential in mafic igneous rocks, basalt, gabbro; common in ultramafic rocks; in some high-grade metamorphic rocks and metamorphosed iron formations.
Anthony et al, Handbook of mineralogy (2001)
Further Information
Mineral information:Augite information at mindat.org
Significant Gem Localities
USA
 
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