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Oxides & Hydroxide

Betpakdalite-CaMg

[Ca₂(H₂O)₁₇Mg(H₂O)₆][Mo⁶⁺₈As⁵⁺₂Fe³⁺₃O₃₆(OH)]
Hardness3.5
Crystal systemMonoclinic
ClassOxides & Hydroxide
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Betpakdalite-CaMg

Betpakdalite-CaMg is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula [Ca₂(H₂O)₁₇Mg(H₂O)₆][Mo⁶⁺₈As⁵⁺₂Fe³⁺₃O₃₆(OH)].

It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Betpakdalite structural group.

Key properties: Mohs hardness 3.5; specific gravity 2.98; Colorless to very pale yellow streak; Vitreous to subadamantine luster; optically biaxial.

IMA symbol Bpd-CaMg, IMA status: approved, named in 2011.

Found in a deep oxidation zone of a dolostone-hosted hydrothermal polymetallic ore deposit, produced through alteration of As, Fe and Mo sulfides by solutions rich in Ca and Mg (Tsumeb, Namibia).

It is found associated with Scorodite, djurleite, powellite, adamite, gerdtremmelite, wulfenite, hidalgoite, chalcocite, digenite, kaolinite, quartz, hematite (Tsumeb, Namibia).

The name refers to the original occurrence in the Bet-Pak-Dal Desert, Kazakhstan. Two suffixes correspond to the dominant cations in the two different types of non-framework cation sites.

Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet. Browse more B minerals or help write this entry.