May 7 2013
Augite is a single chain inosilicate mineral and member of pyroxene group. It was named after the Greek word for luster, based on the appearance of its cleavage surface.
Properties of Augite
The following are the key properties of Augite:
- Cell Data
- Space Group: C2/c
- a = 9.699
- b = 8.844
- c = 5.272
- β = 106.97°
- Z = 4
- Crystal Data
- Monoclinic
- Point Group: 2/m
- 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}
- X-ray Powder Pattern: 2.994 (100), 3.324 (75), 2.949 (65), 2.516 (65), 2.566 (55), 2.134 (35), 2.895 (34)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
| SiO2 |
51.83 |
45.30 |
| CaO |
19.21 |
22.24 |
| MgO |
16 |
11.20 |
| FeO |
7.21 |
5.15 |
| Al2O3 |
3.07 |
6.72 |
| Fe2O3 |
1.38 |
3.98 |
| TiO2 |
0.49 |
4.33 |
| H2O- |
0.47 |
0.15 |
| Na2O |
0.27 |
0.78 |
| MnO |
0.17 |
0.19 |
| H2O+ |
0.11 |
0.05 |
| K2O |
0.02 |
0.18 |
| Total |
100.23 |
100.27 |
- Optical Properties
- Optical Class: Biaxial (+)
- Pleochroism: X = pale green, pale brown, green, greenish yellow; Y = pale brown, pale yellow-green, violet; Z = pale green, grayish green, violet
- Orientation: Y = b; Z ^ c = -35° to -50°; X ^ a = -20° to -35°
- Dispersion: r > v; weak to moderate
- Absorption: Weak; Y > Z > X.
- α = 1.671-1.735
- β = 1.672-1.741
- γ = 1.703{1.774
- 2V(meas.) = 25°-61°
- Estimated Properties
| Electron density |
Bulk density (electron density)=3.37 g/cm3
note: Specific gravity of Augite =3.40 g/cm3 |
| Photoelectric |
PEAugite = 4.80 barns/electron
U= PEAugite x ρElectron density= 16.17 barns/cm3 |
| Fermion index |
Fermion index = 0.02
Boson index = 0.98 |
| Radioactivity |
Augite is not radioactive |
How to Identify Augite
Augite occurs in range of colors from black to dark brown, light brown, green and brown green. It has translucent to opaque appearance with prominent cleavages, vitreous luster and greenish gray streak. It is non-fluorescent and forms massive fibers, granules or columns. Its fractures are brittle producing small, conchoidal fragments. The hardness of augite ranges from 5 to 6.5, and its average density is 3.4 g/cm3.
Global Distribution
Augite is distributed in the following places:
- Arendal, Norway
- Vesuvius, Campania, Italy
- Frascati, Alban Hills, Lazio
- Mt. Monzoni, Val di Fassa, Trentino-Alto Adige
- Traversella, Piedmont
- Mt. Etna, Sicily
- Laacher See, Eifel district, Germany
- Usti nad Labem, Bilina, Czech Republic
- Azores and Cape Verde Islands
- Renfrew and Haliburton Cos., Ontario
- Otter Lake, Pontiac Co.,Quebec
- Franklin and Sterling Hill, Ogdensburg
- Sussex Co., New Jersey
- Diana, Lewis Co., and Fine, St. Lawrence Co., New York
- Tomik, Gilgit district, Pakistan
- Kangan, Andhra Pradesh, India
Occurrence of Augite and Useful Mineral Association
Augite occurs in gabbro, basalt, mafic igneous rocks, metamorphosed iron formations, ultramafic rocks and some high-grade metamorphic rocks. It is closely associated with minerals like pyroxenes, amphiboles, leucite, olivine, labradorite, sanidine and orthoclase.
References