Mogánite Locality: Dakhla-Oued Ed-Dahab Region, Morocco Size: 2.7 x 1.5 x 1.3 cm A sculptural, excellent and rare pseudomorph from this very obscure African locale. The perfectly fossilized spiral Turritella-like snail has been replaced by lustrous, translucent, brown chalcedony and has a coating of white moganite, a very rare SiO2 modification, that is not uncommon as a minor component of finely crystalline chalcedony (as well as chert or flint) (MINDAT) — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Mogánite
A silica polymorph discovered in 1976 — intergrown micro-domains of quartz-like structure, found in volcanic rocks and lunar samples.
Intro adapted from Wikipedia (CC BY-SA).
Mogánite is an IMA-recognized mineral species in the silicate class, with the chemical formula SiO₂·nH₂O.
It crystallizes in the monoclinic crystal system (space group I2/a).
Key properties: Mohs hardness 6; refractive index 1.528; optically biaxial.
IMA symbol Mog, IMA status: approved, named in 1984.