Variable formula
Chemical formula of a mineral that includes all common elemental replacements. For example, the mineral Adamite - Zn2(AsO4)(OH), frequently contains part of the zinc (Zn) replaced by copper (Cu) or cobalt (Co); thus its variable formula is (Zn,Cu,Co)2(AsO4)(OH). In this guide, the variable elements that are not inherent to the mineral are listed with an underline.
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