Typically sourced from Mexico (Santa
Eulalia, Chihuahua), the United States (Franklin, New Jersey), and
China, this is a secondary mineral that forms in the oxidation zone of
zinc deposits, through alteration of primary sulfides (sphalerite) in the
presence of silica. Its name derives from the “hemimorphism” of its
crystals, which have different terminations at each end of the
crystallographic axis. It typically grows as botryoidal or fan-shaped
aggregates, often associated with smithsonite. Hardness 4.5–5 Mohs,
density 3.4–3.5 g/cm³, color ranging from colorless to blue-green, both
piezoelectric and pyroelectric.
A minor zinc ore of historical interest; highly
valued by collectors for its blue-green botryoidal aggregates
resembling small stalactites; occasionally used in jewelry and
decorative objects when found in compact, colorful form.