White crystals of the very rare tantalum mineral calciotantite from one of the few localities known worldwide (Ungursai, Irtysh River, Kalba Range, Eastern Kazakhstan Province, Kazakhstan), associated to minoritary thoreaulite. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Calciotantite
Calciotantite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula CaTa₄O₁₁.
It crystallizes in the hexagonal crystal system (space group P6_322).
Key properties: specific gravity 7.46; Adamantine luster.
IMA symbol Ctan, IMA status: approved, named in 1981.
Found in the albite-spodumene zone of granite pegmatites.
It is found associated with Microlite, scheelite, wodginite, apatite (Mt. Vasin-Myl’k, Russia); cassiterite, lithiotantite, microlite, thoreaulite, cesplumtantite (Manono pegmatite, Congo).
The name refers to CALCIum and TANTalum in the composition.