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Formula: NaCaMg3(AsO4)3
Arsenate, alluaudite group,
alluaudite supergroup
Crystal System: Monoclinic
Specific gravity: 3.915 calculated
Hardness: 3½
Streak: White
Colour: Colourless, pale green, pale yellow, light blue, pale lilac or pink
Environments
Calciojohillerite is a relatively new mineral, approved in 2016 and to date (July 2023) reported only from
the type locality.
Localities
At the type locality, the Arsenatnaya fumarole, Second scoria cone, Northern Breakthrough, Great Fissure eruption,
Tolbachik Volcanic field, Milkovsky District, Kamchatka Krai, Russia, calciojohillerite is one of the major
arsenates in sublimates of the fumarole.
In middle zones of the fumarole, calciojohillerite is associated with
hematite, tenorite,
johillerite, nickenichite,
bradaczekite, badalovite,
tilasite, lammerite,
ericlaxmanite,
aphthitalite group sulphates,
langbeinite,
calciolangbeinite,
anhydrite, sanidine,
fluorophlogopite,
fluoborite, cassiterite,
pseudobrookite, rutile,
sylvite and halite.
In deep zones calciojohillerite occurs in association with
anhydrite, diopside,
hematite, svabite,
berzeliite, schäferite,
forsterite,
magnesioferrite,
ludwigite,
rhabdoborite group fluoroborates,
powellite, baryte,
fluorapatite, udinaite,
arsenudinaite and
paraberzeliite.
Calciojohillerite forms prismatic crystals up to 1 cm long, their aggregates and crystal crusts up to
0.5 m2
(MM 85.2.215-223).
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