White radial aggregates of the rare Be-mineral sphaerobertrandite from Russia (Karnasurt Mountain, Lovozero Massif, Murmansk Oblast, Russian Federation). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Sphaerobertrandite
Sphaerobertrandite is an IMA-recognized mineral species in the silicate class, with the chemical formula Be₃(SiO₄)(OH)₂.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 5; specific gravity 2.46–2.54; White streak; Vitreous luster; optically biaxial.
IMA symbol Sbtd, IMA status: approved, named in 1957.
Found in schlieren-like pegmatite found in eudialyte lujavrite near the margin of poikilitic nepheline-sodalite syenites (Mannepakhk Mountain). In greisen-like metasomatite developed after high-magnesia rocks (Hsianghualing).
It is found associated with Epididymite, eudidymite, aegirine, mangan-neptunite (Lovozero massif); hambergite, analcime, chiavennite (Tvedalen); bromellite (Hsianghualing).
Alludes to the typical spherulitic morphology of its aggregates and its similarity to bertrandite in the main chemical constituents.