Datolite Locality: Futa Pass, Firenzuola, Florence Province, Tuscany, Italy Original description: Beautiful crystal of 6 mm, transparent. Collection and photo o — Photo: Gianfranco Ciccolini · Public domain
Datolite
A calcium boron nesosilicate first described by Esmark in 1806, named for its granular 'divided' texture.
Intro adapted from Wikipedia (CC BY-SA).
Datolite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaB(SiO₄)(OH).
It crystallizes in the monoclinic crystal system (space group P2_1/a). It is a member of the Gadolinite structural group.
Key properties: Mohs hardness 5–5.5; specific gravity 2.96–3; typically colorless or white or yellow or green or brown or pink; white streak; Vitreous, rarely subresinous on fracture surface luster; refractive index 1.651; optically biaxial.
IMA symbol Dat, grandfathered status — known before the IMA’s founding, named in 1806.
Found as a secondary mineral in mafic igneous rocks; in geodes in tuffs; in skarns in limestones; in serpentinites and \hornblende" schists; from some ore veins.
It is found associated with Calcite, prehnite, zeolites, danburite, axinite, garnet.
Its name comes from the Greek to divide, in reference to the granular structure of a massive variety.
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