Richterite

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Richterite
Richterite-mrz156a.jpg
Richterite. Wilberforce, Monmouth Township, Haliburton County, Ontario, Canada.
General
Category Inosilicates
Formula
(repeating unit)
Na(NaCa)Mg5Si8O22(OH)2
Strunz classification 09.DE.20
Identification
Color Brown, yellow, red, or green
Crystal habit Prismatic; acicular or asbestiform
Crystal system Monoclinic
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 [1][2][3][4]

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 aggregates, 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-rish 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[edit]

  • Bonewitz, 2008, Smithsonian Rock and Gem