Red-brown microcrystals of ponomarevite, an extremely rare K-Cu chloride from the famous Tolbachik volcano (Tolbachik Volcano, Kamchatka Krai, Russian Federation) the only known locality and associated to green crystals of klyuchevskite. The ponomarevite crystals are difficult to see in the photo. The sample is stored in a closed vial to avoid decomposition in the air atmosphere. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Klyuchevskite
Klyuchevskite is an IMA-recognized mineral species in the sulfate class, with the chemical formula K₃Cu₃Fe³⁺O₂(SO₄)₄.
It crystallizes in the monoclinic crystal system (space group I2). It is a member of the Klyuchevskite structural group.
Key properties: specific gravity 3–3.15; Pale green streak; Submetallic luster; optically biaxial.
IMA symbol Kyv, IMA status: approved, named in 1987.
Found in cavities in volcanic fumaroles.
It is found associated with Alarsite, fedotovite, lammerite, nabokoite, atlasovite, langbeinite, ponomarevite, tolbachite, kamchatkite, hematite, tenorite.
The name is derived from the locality, as one of the Klyuchevskaya group of volcanoes.