Small white crystal group of sibirskite from Russia (Novofrolovskoye Deposit, Turjinsk, Turya River, Krasnotur'insk, Sverdlovsk Oblast, Russian Federation). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Sibirskite
Sibirskite is an IMA-recognized mineral species in the borate class, with the chemical formula CaH(BO₃).
It crystallizes in the monoclinic crystal system (space group P2_1/a).
Key properties: specific gravity 2.58; Vitreous luster; optically biaxial.
IMA symbol Sib, grandfathered status — known before the IMA’s founding, named in 1962.
Found in veinlets and aggregates in skarns.
It is found associated with Calcite, “chlorite”, pyrite, garnet, vesuvianite, datolite, tourmaline, axinite (Yuliya Svintsovaya deposit, Russia); takedaite, nifontovite, olshanskyite.
The name refers to its first-noted occurrence in Siberia.