Arizona-Sonora Desert Museum Digital Library

Hemimorphite

Hemimorphite, (Zn₄Si₂O₇(OH)₂ . H₂O), Orthorhombic. An ore of zinc. It occurs as prismatic, tabular crystals that terminate at their base by a pyramid and at their top by a flat crystalline boundary - thus the name hemimorphite, for two forms. A common occurrence is as crystal groups that display rounded groups because of divergent orientation. The mineral is also mammillary, stalactitic, and granular. It has a hardness H of 4½ - 5 and a specific gravity of 3.4 – 3.5 g/cc. Its luster is vitreous and color is white, occasionally faintly blue or green. The mineral is transparent and translucent, and it is strongly pyroelectric.

It is distinguished from smithsonite by its crystal aggregates and from prehnite by its greater specific gravity. It is associated with cerussite, anglesite, smithsonite, sphalerite, and galena. It occurs in the lead-zinc-copper-silver deposits of the western cordillera of the United States, e.g., Tintic, Utah; Leadville, Colorado; and in Mexico in the lead-zinc deposits of Chihuahua.

It is known from many sites in Arizona, a summary of which are noted here: Tombstone and Johnson Camp in Cochise County, the Globe-Miami District of Gila County, Morenci in Greenlee County, the Red Cloud Mine of La Paz County, many mines of Pima County that include those of the Empire Mountains, the Waterman Mountains, the Tucson and Sierrita Mountains, and districts of Pinal and Santa Cruz Counties.

Its name stems from the asymmetrical habit of its crystals.

Ref. 1, 2, 4.