Amphibole kaersutite, en provenance de Alleyras (Haute-Loire, France), au Muséum de Nantes — Photo: Koreller · CC BY-SA 4.0
Kaersutite
A dark-brown to black titanium-bearing calcic amphibole — an oxy-amphibole of alkaline igneous rocks.
Intro adapted from Wikipedia (CC BY-SA).
Kaersutite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaCa₂(Mg₃AlTi⁴⁺)(Si₆Al₂)O₂₂O₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Amphibole structural group.
Key properties: Mohs hardness 5–6; specific gravity 3.2–3.28; typically brown or black; white streak; Vitreous luster; refractive index 1.711; optically biaxial.
IMA symbol Krs, IMA status: approved, named in 1893.
Common as phenocrysts in alkalic volcanic rocks; in gabbroic and peridotitic nodules in alkalic basalts; in syenites, monzonites, carbonatite tuffs, and alkalic gabbros.
It is found associated with Titanian augite, rhÄonite, olivine, ilmenite, spinel, plagioclase, titanian pargasite.
The name refers to the occurrence near Qaersut (formerly Kaersut), Greenland.
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