Betpakdalite-NaNa
Betpakdalite-NaNa is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula [Na₂(H₂O)₁₆Na(H₂O)₆][Mo⁶⁺₈As⁵⁺₂Fe³⁺₃O₃₃(OH)₄].
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Betpakdalite structural group.
Key properties: Mohs hardness 3; specific gravity 2.87; Colorless to very pale yellow streak; Vitreous to subadamantine luster; optically biaxial.
IMA symbol Bpd-NaNa, IMA status: approved, named in 2011.
From the upper oxidation zone of a porphyry copper deposit.
It is found associated with Jarosite, iron oxides and oxyhydroxides (e.g., goethite and akaganéite), scorodite, topaz, leightonite.
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.