The mineral augite

	Chemical Formula	(Ca,Na)(Mg,Fe,Al)(Al,Si)₂O₆
	Composition	Silicate of calcium, sodium, magnesium, iron, and aluminum. Some varieties contain titanium.
	Variable Formula	(Ca,Na)(Mg,Fe,Al,Ti)(Al,Si)₂O₆
	Color	Dark green, grayish-green, greenish brown, dark brown, black
	Streak	Light green to colorless
	Hardness	5 - 6
	Crystal Forms and Aggregates	(Monoclinic) Often as prismatic crystals with a rectangular or octagonal cross section. Also occurs in short, stubby crystals, grainy, columnar, massive, fibrous, in twins, and in disordered aggregates of rectangular crystals. Crystals are partially hollow in some localities.
	Transparency	Opaque. Translucent in thin splinters.
	Specific Gravity	3.2 - 3.6
	Luster	Vitreous, submetallic, dull
	Cleavage	1,2 - prismatic at cleavage angles of 87º and 93º (characteristic of minerals in the pyroxene group). May also exhibit parting in one direction.
	Fracture	Uneven to splintery
	Tenacity	Brittle
	In Group	Silicates ; Inosilicates ; Pyroxene group
	All About	Augite is isomorphous with Diopside and Hedenbergite. It is an intermediary member between Diopside and Hedenbergite (which form a series), but contains additional sodium and aluminum impurities. Strictly speaking, Augite is not a single mineral, but a group of closely related minerals identical in structure but containing different percentages of certain elements. However, Augite is scientifically recognized as one mineral species. Augite is an important rock-forming mineral, and large crystals are fairly common. It is the most widespread member of the pyroxene group, and it frequently alters to many other minerals, including Hornblende, Chlorite, and Epidote. An Augite pseudomorph after a mineral in the amphibole group is called "Uralite". Augite usually occurs in dull crystals that are ugly and uninteresting. Occasionally, though, it is found as lustrous, submetallic crystals, which are sought after by mineral collectors. The name Augite is actually derived from the Greek word augites, "brightness", in reference to the bright luster this mineral sometimes exhibits.
	Uses	Augite is only of interest to mineral collectors. Geologists study this mineral to learn more about mineral environments.
	Striking Features	Color, crystal habits, cleavage, and environment
	Popularity (1-4)	2
	Prevalence (1-3)	1
	Demand (1-3)	2
	Distinguishing Similar Minerals	Tourmaline - different cleavage, slightly harder, crystals usually striated Epidote - different cleavage, more translucent, usually heavily striated Diopside and Hedenbergite - lighter in color (otherwise difficult to distinguish) Enstatite - difficult to distinguish Hornblende - has slightly different cleavage angles (otherwise difficult to distinguish) Aegirine - crystals more elongated
	Commonly Occurs With	Serpentine, Calcite, Biotite, Hornblende, Magnetite, Apatite, Albite, Nepheline, Olivine
	Noteworthy Localities	Excellent Augite crystals are found in the Italian volcanoes of Vesuvius, Stromboli, Etna, and Lazio. Good crystals also come from the Bushfield Complex, Transvaal, South Africa; Auvergne, France; and Eifel, Germany. In the U.S., large crystals are found in upstate New York in the St. Lawrence area (Balmat, Pitcairn, DeKalb, Diana, etc.) Crystals similar to those are also found in Canada in Renfrew Co. Another famous area for Augite crystals are the Ramapo Mountains, Orange and Rockland Counties, New York (Hogencamp Mine, Brooks Hollow, and Iona Island). Augite is also found in Franklin, Sussex Co., New Jersey; the Trail Creek area, Grand Co., Colorado; the Stillwater Complex, Montana; and Cedar Butte, near Tillamook, Tillamook Co., Oregon.
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