Richterite
Richterite | |
---|---|
![]() Richterite. Wilberforce, Monmouth Township, Haliburton County, Ontario, Canada. | |
General | |
Category | Inosilicates |
Formula (repeating unit) | Na(NaCa)Mg5Si8O22(OH)2# |
IMA symbol | Rct[1] |
Strunz classification | 9.DE.20 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | C2/m |
Identification | |
Color | Brown, yellow, red, or green |
Crystal habit | Prismatic; acicular or asbestiform |
Twinning | Simple or multiple parallel to {100} |
Cleavage | Perfect |
Fracture | Uneven, brittle |
Mohs scale hardness | 5-6 |
Luster | Vitreous |
Streak | Pale yellow |
Diaphaneity | Transparent to translucent |
Specific gravity | 3.0-3.5 |
Optical properties | Biaxial (-) |
Refractive index | nα = 1.615 nβ = 1.629 nγ = 1.636 |
Birefringence | δ = 0.021 |
Pleochroism | Strong: pale yellow, orange, and red |
2V angle | 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).
References
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85: 291–320.
- ^ Handbook of Mineralogy
- ^ Richterite on Mindat.org
- ^ Richterite data on Webmin
- ^ IMA Master List
- Bonewitz, 2008, Smithsonian Rock and Gem