Dull white masses of the extremely rare mineral sergeevite from the type and only known locality worldwide in Russia (Tyrnyauz Deposit, Baksan Valley, Kabardino-Balkaria, Russian Federation). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Sergeevite
Sergeevite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Ca₂Mg₁₁(CO₃)₉(HCO₃)₄(OH)₄·6H₂O.
It crystallizes in the hexagonal crystal system.
Key properties: Mohs hardness 3.5; specific gravity 2.55–2.87; Dull luster.
IMA symbol Sge, IMA status: approved, named in 1979.
A weathering product of pyroxene–garnet skarn.
It is found associated with Huntite, chrysocolla, chalcanthite, brochantite, malachite, gypsum, epsomite, “limonite”.
The mineral was named to honor Professor Yevgenii Mikhailovich Sergeev (1924–1997), geological engineer, Moscow University, Moscow, Russia.