Chamosite (Var. Thuringite Klementite) - Vielsalm, Stavelot Massif, Luxembourg Province, Belgium - 9cm — Photo: Didier Descouens · CC BY-SA 4.0
Chamosite
Also known as: Chlorite.
The iron end-member of the chlorite group — a hydrous iron-aluminium silicate common in oolitic ironstones and low-grade metamorphic rocks.
Intro adapted from Wikipedia (CC BY-SA).
Chamosite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Fe²⁺,Mg,Al,Fe³⁺)₆(Si,Al)₄O₁₀(OH,O)₈.
It crystallizes in the triclinic crystal system (space group C-1). It is a member of the Chlorite, Clay structural group.
Key properties: Mohs hardness 2.5–3.5; specific gravity 3–3.4; typically green or gray or brown or black; Green to gray streak; Pearly luster; optically biaxial.
IMA symbol Chm, grandfathered status — known before the IMA’s founding, named in 1820.
Found in sedimentary ironstones; authigenically formed under reducing conditions in the presence of decomposed organic material.
It is found associated with Siderite, kaolinite, quartz, magnetite, pyroxenes, plagioclase, olivine, calcite.
The name is derived from the locality at Chamoson, Switzerland.
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