Hillesheimite
Hillesheimite is an IMA-recognized mineral species in the silicate class, with the chemical formula (K,Ca,Ba, )₂(Mg,Fe,Ca, )₂[(Si,Al)₁₃O₂₃(OH)₆](OH)·8H₂O.
It crystallizes in the orthorhombic crystal system (space group Pmmn). It is a member of the Günterblassite structural group.
Key properties: Mohs hardness 4; specific gravity 2.16; White streak; optically biaxial.
IMA symbol Hlh, IMA status: approved, named in 2011.
Encrusts the walls of miarolitic cavities in alkali basalt.
It is found associated with Nepheline, augite, fluorapatite, magnetite, perovskite, priderite, götzenite, lamprophyllite group minerals, åkermanite.
The name refers to the town of Hillesheim, near where the studied samples were collected.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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