Bosoite

bosoite

chibaite

dachiardite

sepiolite

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Formula: SiO2.nCxH2x+2
Oxide
Specific gravity: 2.04 calculated
Hardness: 6½ to 7
Streak: White
Colour: Colourless
Luminescence: Non-fluorescent under UV
Environments

Metamorphic environments
Hydrothermal environments

Bosoite is a rare mineral, approved in 2014, and to date (May 2022) found only at the type locality.

Localities

At the type locality, Arakawa, Minamiboso city, Chiba Prefecture, Japan, bosoite occurs in association with chibaite and as an epitaxial intergrowth on chibaite. The two minerals occur in small quartz and calcite veins partly developed at fault planes in tuffaceous sandstone and mudstone.
The sequence of mineral formation from rim to centre of the vein is generally (1) a very thin layer of clinoptilolite-(Na) and/or opal-A, melanophlogite, and
(2) chibaite, bosoite and calcite.
Melanophlogite was always found as cubic forms of semi-translucent quartz pseudomorphs, with only one exception of an unaltered sample. Many of chibaite ‘crystals’ are also altered and occur as white quartz pseudomorphs. Some parts of the veins are composed of primary quartz grains or microcrystalline chalcedony. Other minerals associated with bosoite are pyrite, dachiardite, sepiolite, gypsum and baryte. The bosoite was formed under low-temperature hydrothermal conditions during diagenesis (MM 84.941–948).

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