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Formula: K3NaCu4O2(SO4)4
Sulphate
Crystal System: Orthorhombic
Specific gravity: 3.23 measured, 3.19 calculated from the empirical formula
Hardness: 2½
Streak: Light green
Colour: Dark green with bluish hue or deep emerald-green
Solubility: Slowly dissolves in pure water
Common impurities: Rb,Cs
Environments
Wulffeite is a relatively new mineral, approved in 2013 and to date (January 2023) reported only from the
Tolbachik Volcanic Field.
Localities
At the type locality, the Arsenatnaya fumarole, Second scoria cone, Northern Breakthrough, Great Fissure eruption,
Tolbachik Volcanic field, Milkovsky District, Kamchatka Krai, Russia, wulffite and
parawulffite were collected from two active, hot fumaroles in the second
scoria cone, formed in 1975. Its fumarole fields are still active; numerous gas vents with temperatures up to 430°C
were observed in 2012–13. Arsenatnaya is a system of numerous mineralised pockets located between blocks of
basalt scoria and volcanic
bombs at depths of 0.3 to 1.0 m from the present-day surface. The sublimate minerals are mainly sulphates,
arsenates and oxides. The temperature measured in pockets with wulffite in 2013 was 360 to 380°C.
Wulffite is common in this fumarole, forming coarse, prismatic, elongated crystals up to 2 mm long and up to
1.2 mm thick, separate or combined in groups up to 1 cm across. Incrustations consisting of crude crystals or, more
often, irregularly shaped grains of wulffite, sometimes together with
euchlorine or fedotovite, on
the surface of basalt scoria
or on tenorite crystal crusts are the most common. Crystals and granular
crusts of aphthitalite with numerous inclusions of separate crystals and
crystal clusters of wulffite are common. Wulffite is also associated with
hematite, langbeinite,
calciolangbeinite, arcanite,
krasheninnikovite,
lammerite, paralammerite,
johillerite, bradaczekite,
urusovite, fluoborite,
copper-bearing gahnite,
arsenic-bearing orthoclase and
fluorophlogopite.
Wulffite and parawulffite are exhalation minerals; it is believed
that they were deposited directly from the gaseous phase as sublimates at temperatures not lower than 360 to 380°C in
the fumaroles and not lower than 620 to 650°C in fumaroles related to the 2012–2013 Tolbachik Fissure Eruption
(CM 52.699-716).
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