Betpakdalite-FeFe
Chemical formula: [Fe<sup>3+</sup><sub>2</sub>(H<sub>2</sub>O)<sub>15</sub>(OH)<sub>2</sub>Fe<sup>3+</sup>(H<sub>2</sub>O)<sub>6</sub>][Mo<sup>6+</sup><sub>8</sub>As<sup>3+</sup><sub>2</sub>Fe<sup>3+</sup><sub>3</sub>O<sub>37</sub>]