Dargaite
A rare barium-calcium silicate-sulfate from Israel's Hatrurim complex — the barium analogue of nabimusaite.
Intro adapted from Wikipedia (CC BY-SA).
Dargaite is an IMA-recognized mineral species in the silicate class, with the chemical formula BaCa₁₂(SiO₄)₄(SO₄)₂O₃.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Nabimusaite structural group.
Key properties: Mohs hardness 4.5–5.5; specific gravity 3.235; White streak; Vitreous luster; optically uniaxial.
IMA symbol Drg, IMA status: approved, named in 2015.
Pyrometamorphic by-product of gases, fluids and melts transforming earlier mineral associations (larnite rocks) at ∼900 flC (Israel). In an altered carbonate xenolith from the lava bed of the Shadi-Khokh volcano (Southern Ossetia).
It is found associated with Larnite, fluorellestadite-fluorapatite, brownmillerite, fluormayenite-fluorkyuygenite, ye’elimite, ternesite, shulamitite, periclase (Hahal Darga).
The name refers to the canyon (Hahal) Darga, near where studied specimens were collected.