Article
Article
Hemimorphite
Article By:
Hurlbut, Cornelius S., Jr. Department of Geological Sciences, Harvard University, Cambridge, Massachusetts.
Last reviewed:May 2021
DOI:https://doi.org/10.1036/1097-8542.313400
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- Hemimorphite, published November 2019:Download PDF
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A mineral sorosilicate having the composition Zn4Si2O7(OH)2 · H2O; an ore of zinc. Hemimorphite crystallizes in the orthorhombic system, pyramidal class, and thus the prismatic crystals have different forms at top and bottom. Also, as a result of the symmetry, the vertical axis is polar. And crystals display the properties of pyroelectricity and piezoelectricity. There is perfect prismatic cleavage. Botryoidal and staclactic aggregates, showing a crystalline surface and frequently impure, are common. Crystals are usually colorless and the aggregates white, but in some cases there are faint shades of green, yellow, and blue (see illustration). The mineral has a vitreous luster, a hardness of 4½ to 5 on Mohs scale, and a specific gravity of 3.45. Hemimorphite frequently resembles the zinc carbonate, or smithsonite, but can be distinguished by the reaction with hydrochloric acid. Hemimorphite is slowly soluble but smithsonite effervesces in cold acid. The mineral known as calamine, in actuality, consists of both hemimorphite and smithsonite. See also: Piezoelectricity; Pyroelectricity; Smithsonite
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