Lemon yellow crystals of the rare molybdenium mineral betpakdalite-NaCa from the type and only known locality worldwide: Kyzylsai Mo U Deposit, Chu-Ili Mountains, Almaty Province, Kazakhstan. This is part of the holotype material studied by the author. — Photo: David Hospital · CC BY-SA 4.0
Betpakdalite-NaCa
Betpakdalite-NaCa is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula [Na₂(H₂O)₁₇Ca(H₂O)₆][Mo⁶⁺₈As⁵⁺₂Fe³⁺₃O₃₄(OH)₃].
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Betpakdalite structural group.
Key properties: specific gravity 2.02; Dull luster.
IMA symbol Bpd-NaCa, IMA status: approved, named in 1971.
The name refers to the Bet-Pak-Dal Desert, Kazakhstan. Two suffixes correspond to the dominant cations in the two different types of non-framework cation sites.