Why is arsenious oxide also called white arsenic?

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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.

Arsenious oxide ( $A s_{4} O_{6}$ ) is commonly referred to as "white arsenic" because it is the oxide formed when arsenic or arsenic-containing ores are heated in air. This process produces a vapor that is collected and condensed into a white, powdery substance.1

This compound is a primary commercial form of arsenic, serving as the starting material for most other arsenic compounds. It is obtained as a by-product during the roasting of various metal ores, such as copper and lead, as well as arsenopyrite and arsenic sulfide ores. Beyond its role in chemical production, white arsenic has historically been utilized in pesticides, as a glass decolorizer, and as a preservative for hides.1