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Formula: K3Cu3Fe3+O2(SO4)4
Anhydrous sulphate
Crystal System: Monoclinic
Specific gravity: 3.00 to 3.15 measured, 2.98 calculated
Hardness: 3½
Streak: Pale green
Colour: Dark green to olive-green
Solubility: Readily soluble in water and in weak acid (1:20)
Common impurities: Pb
Environments
Although klyuchevskite was approved as long ago as 1987, to date (June 2025) it has been reported
only from the Great Fissure eruption. It hydrates in air in one week, and is stable in air up to 625°C
(AM 75.1211-1212)
Localities
At the type locality, the Great Fissure eruption, Tolbachik volcano, Kamchatka Krai, Russia, klyuchevskite
occurs in cavities in volcanic fumaroles, associated with alarsite,
fedotovite, lammerite,
nabokoite, atlasovite,
langbeinite, ponomarevite,
tolbachite, kamchatkite,
hematite and tenorite
(HOM). The klyuchevskite occurs as crystals in orientated aggregates, acicular, up to 0.1 mm long and not
thicker than 0.01 mm, in cavities and fissures in massive sublimates composed of
kamchatkite, ponomarevite
and hematite
(AM 75.1211-1212).
Klyuchevskite from the Great Fissure eruption -
Image
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