Olivenite

Olivenite is a copper arsenate mineral that occurs as olive-green to yellow-green crystals and masses. It is commonly described as a copper arsenate hydroxide with water incorporated in its structure, and it is typically represented as a copper arsenate with varying water content. The mineral crystallizes in the monoclinic system and forms prismatic to tabular crystals or grows in compact to massive aggregates. It has a vitreous to resinous luster and a greenish streak; its hardness ranges around 3.5 to 4 on the Mohs scale, and its specific gravity is about 4.0 to 4.4.

Olivenite forms in the oxidized zones of copper-bearing ore deposits and is frequently found in association with other secondary minerals such as malachite, azurite, chrysocolla, goethite, and limonite. It can occur as replacement products in copper sulfide districts and in weathering profiles where copper arsenates accumulate.

The name olivenite derives from its distinctive olive-green color. The mineral was described in the 19th century and has since been found at numerous localities around the world. Notable occurrences include mining districts in Bisbee, Arizona; Tsumeb, Namibia; Freiberg, Germany; and the Ojuela mine in Mexico.

Because olivenite is a secondary mineral with variable composition, its exact chemical formula can vary, and water content may differ among samples. It holds little to no economic value as an ore, but it is of interest to mineral collectors and researchers studying copper-arsenate minerals.