Armenite
BaCa2(Si9Al6)O30 • 2H2O [CNMNC approved formula]
Named after its locality: Armen Mine, Kongsberg, Norway.
| IMA status : | Valid species (Pre-IMA 1939) Grandfathered |
| CLASSIFICATION | |
| Dana (8th edition) : |
63.02.01b.01 |
| (63) Cyclosilicate Condensed Rings | |
| (63.02) 6-membered rings | |
| (63.02.01b) Milarite - Osumilite group | |
| Nickel-Strunz (10th edition) : |
09.CM.05 |
| (09) Silicates | |
| (09.C) Cyclosilicates | |
| (09.CM) [Si6O18]12- 6-membered double rings (sechser-Doppelringe) | |
| Crystal system: | Orthorhombic System |
| Point group (H-M): | mm2 — pyramidal |
| Unit cell: | a = 13.87 Å, b = 18.66 Å, c = 10.70 Å |
| Crystal Habit: | Sheaves of prismatic crystals, with individuals to 2.5 cm. |
| Twinning: | complex, showing sectored triplets, may be lamellar |
| Color: | Grayish green, colorless |
| Diaphaneity: | Translucent |
| Luster: | Vitreous |
| Hardness (Mohs): | 7 - 8 |
| Measured Density: | 2.75 g/cm3 |
| Cleavage: | 2; {010} perfect, {110} distinct |
| Tenacity: | Brittle |
| Streak: | White |
| Geologic Setting: | In calcite veins (Kongsberg, Norway); in manganese-metasomatized diorite included in later granodiorite (Remigny, Canada). |
| Mineral Association: | Axinite, pyrrhotite, quartz (Kongsberg, Norway); albite, manganiferous zoisite, piemontite, prehnite, epidote, muscovite (Remigny, Canada); celsian, bytownite (Broken Hill, Australia) |
| Other Properties: | Gemstone Extremely Rare. |
Origin: Simplon Pass, Brig, Valais, SwitzerlandSample size: Microscopic image
Photo and Owner: Lou Perloff
Origin: Simplon Pass, Wasen Alps, Valais, SwitzerlandSample size: 3.2 x 2.2 x 1.5 cm
Photo: Rob Lavinsky
(zoom-in of above)