Outstanding brown crystals of the very rare mineral fedorovskite from the type locality in Buryatia (Solongo, Ozernoe Area, Buryatia Republic, Russian Federation). Ex.Dr.Hartel collection with label included — Photo: David Hospital · CC BY-SA 4.0
Fedorovskite
Fedorovskite is an IMA-recognized mineral species in the borate class, with the chemical formula Ca₂Mg₂B₄O₇(OH)₆.
It crystallizes in the orthorhombic crystal system (space group Pbam).
Key properties: Mohs hardness 4.5; specific gravity 2.65; optically biaxial.
IMA symbol Fdo, IMA status: approved, named in 1975.
Found in veinlets in a skarn-type boron deposit.
It is found associated with Sakhaite, frolovite, uralborite, szaibélyite, datolite.
The mineral was named to honor Nikolai Mikhailovich Fedorovskii (1886–1956), eminent crystallographer and founder of the Russian Research Institute of Mineral Resources, Moscow, Russia.