Arsenate mineral
An arsenate mineral contains arsenate anions, AsO₄³⁻, in its crystal structure, commonly combined with metals such as copper, lead, or iron.
Arsenate: The AsO₄³⁻ oxyanion, in which arsenic is bonded to four oxygen atoms. This anion is the defining structural unit shared by arsenate minerals.
Adamite: A zinc arsenate mineral, Zn₂AsO₄OH, commonly found in oxidized ore deposits. Its zinc-rich composition exemplifies arsenates formed during ore oxidation.
Oxidation zone: The near-surface part of an ore deposit altered by oxygen-rich groundwater and weathering. Oxidizing conditions can convert arsenic-bearing ores into secondary arsenate minerals.
Arsenic contamination: The presence of harmful concentrations of arsenic in environmental media such as water, soil, or air. Weathering or dissolution of arsenate minerals can affect arsenic concentrations in surrounding environments.
Arsenic speciation: The identification of arsenic's chemical forms and oxidation states in a sample. Speciation determines whether arsenic occurs as mineral-bound arsenate or more mobile dissolved forms.
Phosphate mineral: A mineral containing phosphate anions, PO₄³⁻, in its structure. Phosphate and arsenate anions have similar shapes and charges, but different central elements.
Olivenite: A copper arsenate hydroxide mineral with the formula Cu₂AsO₄OH. It illustrates how copper can combine with arsenate in a distinct mineral structure.
Supergene enrichment: The redistribution and concentration of metals near Earth's surface by weathering and groundwater. Groundwater moves metals and arsenic through the zones where secondary arsenates form.
Acid mine drainage: Acidic, metal-rich water produced when sulfide minerals react with oxygen and water. Mine drainage can mobilize arsenic and alter conditions that control arsenate precipitation.
Arsenic biogeochemistry: The interactions of arsenic with organisms, minerals, water, and chemical processes in the environment. Biological and geochemical changes can reshape arsenate minerals and redistribute their arsenic.