Hemimorphite on Limonite Gossan

Physical Properties

Hardness: 4.5-5 (Mohs scale); Color: Colorless to white/pale brown crystals; Luster: Vitreous to pearly; Crystal structure: Orthorhombic (hemimorphic crystals); Cleavage: Perfect on {010}; Specific Gravity: 3.4-3.5

Formation & Geological History

Formed in the oxidized zones of zinc-bearing ore deposits (gossans). It is a secondary mineral resulting from the weathering of primary minerals like sphalerite in the presence of silicate-rich fluids.

Uses & Applications

Historical source of zinc ore (known as 'calamine'); currently used primarily as a collector's mineral specimen and occasionally as a minor gemstone for cabochons.

Geological Facts

The name comes from its 'hemimorphic' crystal habit, meaning the two ends of the crystal are terminated with different faces. It is pyroelectric, meaning it develops an electrical charge when heated.

Field Identification & Locations

Identify by its tabular crystals and association with rusty, iron-rich 'gossan' matrix (limonite). Commonly found in Mapimí (Mexico), Tsumeb (Namibia), and Arizona (USA). Collectors look for well-defined crystal sharp faces against the contrasting dark matrix.

Identified on: 4/14/2026

Mode: Standard