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Silicate

Offretite

KCaMg(Si₁₃Al₅)O₃₆·15H₂O
Hardness4
Crystal systemHexagonal
ClassSilicate
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Offretite specimen

Offretite (Field of view 3 mm) Locality: Vinařice, Kladno, Central Bohemia Region, Bohemia (Böhmen; Boehmen), Czech Republic Original description: Transparent crystals Offretite on matrix; Photo and collection Fernando Brederodes. — Photo: Fernando Brederodes · Public domain

Offretite

Offretite is an IMA-recognized mineral species in the silicate class, with the chemical formula KCaMg(Si₁₃Al₅)O₃₆·15H₂O.

It crystallizes in the hexagonal crystal system (space group P-6m2).

Key properties: Mohs hardness 4; specific gravity 2.13; Vitreous luster; optically uniaxial.

IMA symbol Off, IMA status: approved, named in 1890.

Lining cavities in basalt.

It is found associated with Zeolites, especially erionite, levyne, celadonite, montmorillonite.

The name refers to Professor Albert Jules Joseph Offret (1857{?), of Lyons, France.

Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet. Browse more O minerals or help write this entry.