Kaersutite - Encyclopedia

    Class : Silicates
    Subclass : Inosilicates
    Crystal system : Monoclinic
    Chemistry : NaCa₂Mg₄Ti(Si₆Al₂)O₂₂(OH)₂
    Rarity : Rare

Kaersutite is a sodium, calcium, titanium and magnesium amphibole, formerly considered a variety of hornblende. It is now recognized as a mineral and forms a continuous series with ferro-kaersutite, its iron-bearing equivalent. It is a volcanic amphibole, present in the form of phenocrysts in alkaline volcanic rocks (trachytes and phonolites), in peridotite and gabbro nodules of alkaline basalts and also in syenites, more rarely in monzonites. Basaltic hornblende, rich in titanium and brown-black in color, is most often a ferrohornblende or a kaersutite, the distinction between the two requiring efficient analytical means. Its name comes from its locality of discovery : Kaersut (Greenland). Kaersutite forms often elongated or stocky prisms with a pseudohexagonal section, rarely doubly-terminated, with frequently rounded edges of brown-black color, rarely orange. Kaersutite is also common in masses or aggregates that are more or less fibrous to bacillary, sometimes grainy. The color is usually black-brown.

Main photo : 18 cm kaersutite from Vlcí Hora, Cernosín, Czech Republic © M. Filippi

Single or multiple twins parallel to {100} as well as a star twin are known.

No fakes recorded for this mineral species.