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Formula: SiO2.nCxH2x+2
Oxide
Crystal System: Hexagonal
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 2024) 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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