Sénarmontite

Sénarmontite is an extremely rare mineral and gem. Crystals are very scarce and usually small. Sénarmontite forms excellent octahedral crystals that can be transparent and colorless to gray. It is a very soft (2.0 – 2.5) but dense (5.2 – 5.3) mineral often with an adamantine luster.

The only source of gem quality crystals is the Djebel Haminate Mine, Ain Beida, Constantine Province, Algeria.

Formula: Sb2O3
Antimony(III) Oxide
Crystallography: Isometric – Hexoctahedral
Crystal Habit: Commonly as octahedra, to 3 cm, which may be modified by the cube or dodecahedron; in crusts, granular massive.
Twinning: None

 

Cleavage: [111] Poor/Indistinct in traces
Fracture: Irregular/Uneven
Tenacity: Very Brittle
Hardness (Mohs): 2.0 – 2.5
Density: 5.2 – 5.3 (g/cm3)
Luminescence: None
Radioactivity: Not Radioactive

 

Color: Colorless, White, Gray
Transparency: Translucent to Transparent
Luster: Adamantine, Sub-Adamantine, Resinous
Refractive Index: 2.087  Isotropic
Birefringence: 0.0  (Isotropic)
Pleochroism: None
Anisotrophism: Strong anomalous anisotropism, sectored or zoned.