Very big single crystal of the rare mineral Oxo-magnesio-hastingsite (IMA 2011-035, but approved in 2013) from the fourth locality worldwide: Dolánky, Ohníč, Teplice, Ústí Region, Bohemia, Czech Republic. — Photo: David Hospital · CC BY-SA 4.0
Magnesio-hastingsite
Magnesio-hastingsite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaCa₂(Mg₄Fe³⁺)(Si₆Al₂)O₂₂(OH)₂.
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 3.18–3.22; [Vitreous.] luster; optically biaxial.
IMA symbol Mhst, IMA status: approved, named in 1928.
Found in alkalic basalts; in andesites, latites, tephrites, and their tuffs; in carbonatites.
It is found associated with Olivine, plagioclase, pyroxenes.
The name refers to magnesium in its composition and relation to hastingsite.