[{"from": "human", "value": "Design a molecule that meets the criteria outlined in the description. The molecule is a mineral with formula of Fe2+Fe3+2S4. The corresponding IMA (International Mineralogical Association) number is IMA1963-007. The IMA symbol is Grg."}, {"from": "gpt", "value": "[S-2].[S-2].[S-2].[S-2].[Fe+2].[Fe+3].[Fe+3]"}]