Augite
Current inventory:  0 gems
 

  
Augite was named by Abraham G. Werner in 1792 from the Greek "auge" for "shine" or "luster," in allusion to the appearance of its cleavage surfaces.

Discovered in 1792; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Ca,Na)(Mg,Fe,Al,Ti)(Si,Al)₂O₆

Calcium Sodium Magnesium Iron Aluminum Titanium Silicate

Molecular Weight:

236.35 gm

Composition:

Sodium

0.97 %

Na

1.31 %

Na₂O

Calcium

15.26 %

Ca

21.35 %

CaO

Magnesium

9.26 %

Mg

15.35 %

MgO

Titanium

2.03 %

Ti

3.38 %

TiO₂

Aluminum

4.57 %

Al

8.63 %

Al₂O₃

Iron

4.73 %

Fe

6.08 %

FeO

Silicon

22.58 %

Si

48.30 %

SiO₂

Oxygen

40.62 %

O

100.00 %

104.40 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/F.01-90

Nickel-Strunz 10th Ed. ID:

9.DA.15

9 : SILICATES (Germanates)
D : Inosilicates
A : Inosilicates with 2-periodic single chains, Si₂O₆; pyroxene family

Related to:

Pyroxene Group. Clinopyroxene Subgroup.

Members of Group:

Pyroxene Group: Canaanite, Clinopyroxene Subgroup, Orthopyroxene Subgroup

Members of Subgroup:

Clinopyroxene Subgroup: Aegirine, Augite, Clinoenstatite, Clinoferrosilite, Diopside, Essenite, Grossmanite, Hedenbergite, Jadeite, Jervisite, Johannsenite, Kanoite, Kosmochlor, Kushiroite, Namansilite, Natalyite, Petedunnite, Pigeonite, Spodumene

Varieties:

Asteroite, Fassaite, Jeffersonite, Korea-Augite, Soda-Augite, Titanian Augite

Synonyms:

Basaltine, Hedenbergite-Ågirin, Violatite, Volcanic Shorl, Volcanite (of Delamétherie)

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Stubby prismatic crystals, square or octagonal in section, to 10 cm; elongated || [001], acicular, skeletal, dendritic. Exsolution lamellae and overgrowths common.

Twinning:

Simple or multiple on {100}, common; also on {001}.

Physical Properties

Cleavage:

Good on {110}, (110) ^ (110) ~87°; partings on {100} and {010}

Fracture:

Irregular/Uneven to Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5 - 6.0

Density:

3.19 - 3.56 (g/cm³)

Luminescence:

Not Fluorescent

Radioactivity:

Not Radioactive

Optical Properties

Color:

Black, brown, greenish, violet-brown; in thin section, colorless to gray; clear cores zoned to dark rims common, also oscillatory and sector zoning.

Transparency:

Transparent to Translucent

Luster:

Vitreous, resinous to dull

Refractive Index:

1.575 - 1.584  Biaxial ( + ) 

Birefringence:

0.009

Dispersion:

Weak to moderate; r > v

Pleochroism:

X = pale green, pale brown, green, greenish yellow; Y = pale brown, pale yellow-green, violet; Z = pale green, grayish green, violet

Occurances

Geological Setting:

Essential in mafic igneous rocks, basalt, gabbro; common in ultramafic rocks; in some high-grade metamorphic rocks and metamorphosed iron formations.

Common Associations:

Orthoclase, Sanidine, Labradorite, Olivine, Leucite, amphiboles, pyroxenes

Common Impurities:

Ti, Cr, Na, Mn, K

Type Locality:

Unknown

Year Discovered:

1792

View mineral photos:

Augite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Augite was named by Abraham G. Werner in 1792 from the Greek "auge" for "shine" or "luster," in allusion to the relatively high luster of its cleavage surfaces. Augite is an important rock-forming mineral in many igneous rocks, especially in gabbros and basalts, and is also found in some hydrothermal metamorphic rocks. Augite is a member of the Pyroxene Group and Clinopyroxene Subgroup that includes Aegirine, Augite, Diopside, Hedenbergite, Jadeite, Johannsenite and Spodumene. Augite is found in colors of black, greenish black, brown and violet-brown. It is a relatively rare gem and is mostly for collectors of the unusual.

Distribution: Widespread; only a few classic localities, much studied or providing fine examples, are listed. From Arendal, Norway. In Italy, from Vesuvius, Campania; around Frascati, Alban Hills, Lazio; on Mt. Monzoni, Val di Fassa, Trentino-Alto Adige; at Traversella, Piedmont; and on Mt. Etna, Sicily. Around the Laacher See, Eifel district, Germany. At Ústí nad Lábem (Aussig), Bílina, and Vlcí Hora, near Cernosín, Czech Republic. On the Azores and Cape Verde Islands. In Canada, from Renfrew and Haliburton Counties, Ontario; at Otter Lake, Pontiac County, Quebec; and many other localities. In the USA, from Franklin and Sterling Hill, Ogdensburg, Sussex County, New Jersey; and at Diana, Lewis County, and Fine, St. Lawrence County, New York. From Tomik, Gilgit district, Pakistan. At Kangan, Andhra Pradesh, India.
 

  
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