Hielscherite Field of view: 3 mm Locality: Graulai Quarry (TL), Hillesheim, Gerolstein, Vulkaneifel, Rhineland-Palatinate, Germany — Photo: Henk Smeets – tomeikminerals.com · CC BY 4.0
Hielscherite
Hielscherite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₆Si₂[(SO₄)₂(SO₃)₂(OH)₁₂]·22H₂O.
It crystallizes in the hexagonal crystal system (space group P6_3). It is a member of the Ettringite structural group.
Key properties: Mohs hardness 2–2.5; specific gravity 1.82; White streak; Vitreous; silky aggregates luster; optically uniaxial.
IMA symbol Hsc, IMA status: approved, named in 2011.
Found in miarolitic cavities in alkaline basalt or also in xenoliths in volcanic glass.
It is found associated with Diopside, nepheline, fluorapatite, magnetite, phillipsite-K, chabazite-Ca, gypsum, gismondine.
The mineral was named to honor German mineral collector Klaus Hielscher (b. 1957) from Steinbach, Hessen, a specialist in the mineralogy of the Zeilberg basalt quarry in Franconia, Bavaria, Germany.