Richterite
Richterite is closely related to Tremolite. Richterite is the sodium-rich version of Tremolite which is Calcium rich. Richterite is a member of the Calcic Clino-Amphibole Subgroup of the Amphibole Group of minerals that includes Actinolite, Ferro-edenite, Kaersutite, Pargasite, Richterite, and Tremolite. The Amphibole Group is an extensive and complex group of minerals currently divided into several sub-groups. Richterite is usually opaque to translucent and clean, facetable crystals are very rare and small.
There are small, gemmy, yellow crystals found in Badakhshan Province, Afghanistan but these are quite rare. Richterite is also found in the meteorite field at Canyon Diablo, Arizona, USA.
| Category: | Inosilicates |
| Formula: | Na(NaCa)Mg5Si8O22(OH)2 |
| Crystallography: | Monoclinic – Prismatic |
| Crystal Habit: | Crystals commonly prismatic, flattened along [100], rarely doubly terminated, to 15 cm; acicular or asbestiform. |
| Twinning: | Simple or multiple twinning on [100]. |
| Cleavage: | [110] Perfect; partings on [100] and [001] |
| Fracture: | Irregular/Uneven |
| Tenacity: | Brittle |
| Hardness (Mohs): | 5.0 – 6.0 |
| Density: | 3.00- 3.05 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Blue, Brown, Brown Red, Gray Violet, Yellow |
| Transparency: | Translucent to Transparent |
| Luster: | Vitreous |
| Refractive Index: | 1.615 – 1.636 Biaxial ( – ) |
| Birefringence: | 0.0210 |
| Dispersion: | Strong; r < v |
| Pleochroism: | Strong; in pale yellows, orange, and red. |
