White core of tsepinite-Na with an epitaxial growth of orange Labuntsovite-Mn crystal from the famous Aris Quarry (Windhoek, Khomas Region, Namibia). — Photo: David Hospital · CC BY-SA 4.0
Tsepinite-Na
Tsepinite-Na is an IMA-recognized mineral species in the silicate class, with the chemical formula (Na,H₃O,K,Sr,Ba, )₂(Ti,Nb)₂(Si₄O₁₂)(OH,O)₂·3H₂O.
It crystallizes in the monoclinic crystal system (space group Cm). It is a member of the Labuntsovite structural group.
Key properties: Mohs hardness 5; specific gravity 2.74; White streak; Vitreous luster; optically biaxial.
IMA symbol Tsp-Na, IMA status: approved, named in 2000.
Found in cavities formed by hydrothermal alteration of alkaline pegmatite.
It is found associated with Microcline, aegirine, analcime, natrolite, catapleiite, apophyllite, labuntsovite-Mn (Mt. Khibinpakhchorr); microcline, aegirine, magnesio-arfvedsonite.
The mineral was named to honor Russian microprobe analyst Anatoliy I. Tsepin (b. 1946) and the suffix indicates the Na-dominant analog of tsepinite-K and tsepinite-Ca.