Outstanding white crystals of the extremely rare mineral vimsite, a calcium borate, from the type locality (Solongo, Buryatia, Eastern Siberia, Russian Federation) and one of the only two known worldwide localities, associated to minoritary sakhaite. — Photo: David Hospital · CC BY-SA 4.0
Vimsite
Vimsite is an IMA-recognized mineral species in the borate class, with the chemical formula CaB₂O₂(OH)₄.
It crystallizes in the monoclinic crystal system (space group C2/c).
Key properties: Mohs hardness 4; specific gravity 2.54; Vitreous luster; optically biaxial.
IMA symbol Vim, IMA status: approved, named in 1968.
Found in boron-rich copper-bearing skarn (Novofrolovskoye deposit, Russia); in iron-bearing skarn (Solongo deposit, Russia).
It is found associated with uralborite, andradite–grossular, calciborite, sibirskite, magnetite (Novofrolovskoye deposit, Russia); frolovite (Solongo deposit, Russia).
The name refers to the 50th anniversary of the All-Union Scientific Research Institute of Mineral Resources [an acronym for Vses. Nauch.-Issled. Inst. Mineral. Syr’ya], Moscow, Russia.