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What happens when arsenopyrite is heated without air?

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A labeled diagram of the periodic table entry for arsenic, showing its atomic number 33, symbol As, atomic weight 74.921595, electron configuration, and classification as an other nonmetal. Additional icons indicate arsenic is solid at room temperature, has a rhombohedral crystal structure, and weakly acidic oxides. — arsenic Properties of arsenic.

When arsenopyrite—the most common ore of arsenic—is heated to temperatures between 650 and 700 °C in the absence of air, it produces metallic arsenic.1

This process differs significantly from heating the mineral in the presence of air, which causes the arsenic to react with oxygen to form the easily sublimed oxide $A s_{4} O_{6}$ , commonly known as "white arsenic".1