| Richterite | |
| Category: | Inosilicates |
| Formula: | Na(NaCa)Mg5Si8O22(OH)2# |
| Imasymbol: | Rct[1] |
| Strunz: | 9.DE.20 |
| System: | Monoclinic |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | C2/m |
| Color: | Brown, yellow, red, or green |
| Habit: | Prismatic; acicular or asbestiform |
| Twinning: | Simple or multiple parallel to |
| Mohs: | 5–6 |
| Cleavage: | Perfect |
| Fracture: | Uneven, brittle |
| Luster: | Vitreous |
| Streak: | Pale yellow |
| Gravity: | 3.0–3.5 |
| Diaphaneity: | Transparent to translucent |
| Opticalprop: | Biaxial (−) |
| Refractive: | nα = 1.615 nβ = 1.629 nγ = 1.636 |
| Birefringence: | δ = 0.021 |
| Pleochroism: | Strong: pale yellow, orange, and red |
| 2V: | 68° measured |
| References: | [2] [3] [4] [5] |
Richterite is a sodium calcium magnesium silicate mineral belonging to the amphibole group. If iron replaces the magnesium within the structure of the mineral, it is called ferrorichterite; if fluorine replaces the hydroxyl, it is called fluororichterite. Richterite crystals are long and prismatic, or prismatic to fibrous aggregate, or rock-bound crystals. Colors of richterite range from brown, grayish-brown, yellow, brownish- to rose-red, or pale to dark green. Richterite occurs in thermally metamorphosed limestones in contact metamorphic zones. It also occurs as a hydrothermal product in mafic igneous rocks, and in manganese-rich ore deposits. Localities include Mont-Saint-Hilaire, Quebec, and Wilberforce and Tory Hill, Ontario, Canada; Långban and Pajsberg, Sweden; West Kimberley, Western Australia; Sanka, Myanmar; and, in the US, at Iron Hill, Colorado; Leucite Hills, Wyoming; and Libby, Montana. The mineral was named in 1865 for the German mineralogist Hieronymous Theodor Richter (1824–1898).