May 29 2014
Armenite is a member of the osumilite group of minerals. It was named after the Armen mine in Kongsberg, Norway.
The mineral was first collected by O.A. Corneliussen in 1877, who stored the sample labeled as “epidote” in the University of Oslo. Later, in February 1939, Henrich Neumann re-discovered it and recognized it as a new mineral.
Properties of Armenite
The following are the key properties of Armenite:
- Cell Data
- Space Group: Pnna
- a = 13.874(2)
- b = 18.660(2)
- c = 10.698(1)
- Z = 4
- Crystal Data
- Orthorhombic, pseudohexagonal
- Point Group: 2/m 2/m 2/m
- Sheaves of prismatic crystals, with individuals to 2.5cm
- Twinning: Complex, showing sectored triplets, may be lamellar
- X-ray Powder Pattern: 3.86 (100), 3.41 (90), 2.91 (90), 6.94 (80), 2.78 (80), 4.25 (65), 9.31 (55)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| SiO2 |
46.18 |
47.6 |
47.10 |
| Al2O3 |
27.52 |
27 |
26.64 |
| BaO |
12.37 |
12.05 |
13.35 |
| CaO |
9.99 |
9.50 |
9.77 |
| H2O+ |
3.41 |
- |
- |
| Na2O |
0.16 |
0.36 |
- |
| K2O |
0.13 |
0.15 |
- |
| H2O- |
0.11 |
- |
- |
| SrO |
0.04 |
0.62 |
- |
| H2O |
- |
2.90 |
3.14 |
| CO2 |
- |
0.31 |
- |
| Total |
99.91 |
100.49 |
100 |
- Optical Properties
- Optical Class: Biaxial (-), with uniaxial (-) domains
- Orientation: X = c; Z = b
- α = 1.550-1.551
- β = 1.557-1.559
- γ = 1.559-1.562
- 2V(meas.) = 60° - 65°
- 2V(calc.) = 57.8°
- Estimated Properties
| Electron density |
Bulk density (electron density) = 2.68 g/cm3
note: Specific gravity of Armenite = 2.75 g/cm3 |
| Photoelectric |
PEArmenite = 51.31 barns/electron
U = PEArmenite x ρElectron density = 137.65 barns/cm3 |
| Fermion index |
Fermion index = 0.03
Boson index = 0.97 |
Radioactivity
|
Armenite is not radioactive
|
How to Identify Armenite
Armenite is commonly available in colorless form, or gray-white/white color forms. It has a translucent appearance, with white streak, and vitreous luster. Its fractures are brittle, generally exhibited by most of the non-metallic minerals and glasses.
Its relative hardness is 7.5 and density is 2.76 g/cm3.
Global Distribution
Armenite is distributed in the following places:
- Armen mine, near Kongsberg, Norway
- Su Zurfuru mine, Fluminese, Sardinia, Italy
- Wasenalp, near Simplon, Valais, Switzerland
- Coire Loch Kander, 11km south-south-east of Braemar, Scotland
- Chvaletice, Czech Republic
- Remigny, Quebec, Canada
- North Bend, King Co. Washington, USA
- Broken Hill and Pernamoota, 30km north of Broken Hill, New South Wales, Australia
Occurrence of Armenite and Useful Mineral Association
Armenite occurs in calcite veins (Kongsberg, Norway) and manganese-metasomatized diorite, included in later granodiorite (Remigny, Canada).
Armenite is closely associated with bytownite, celsian, muscovite, epidote, prehnite, piemontite, manganiferous zoisite, albite, quartz, pyrrhotite, and axinite.
References