Calciosamarskite
Calciosamarskite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Ca,Fe,Y)(Nb,Ta,Ti)O₄.
It crystallizes in the monoclinic crystal system. It is a member of the Samarskite structural group.
Key properties: Mohs hardness 5–6; specific gravity 5.8; Brown to black streak; Vitreous luster.
IMA symbol Csmk, grandfathered status — known before the IMA’s founding, named in 1928.
An accessory mineral in RE-rich granite pegmatites, common but not abundant.
It is found associated with Columbite, zircon, monazite, uraninite, aeschynite, magnetite, albite, topaz, beryl, garnet, muscovite, biotite.
The mineral was named to honor Colonel Vasilii Evgrafovich von Samarskii-Bykhovets (1803-1870), Chief of Staff of the Russian Corps of Mining Engineers. The prefix, calcio.