Hemimorphite Gems
Hemimorphite is a zinc-containing mineral that was once known as calamine. In 1803 the British chemist and mineralogist James Smithson discovered that there were two different minerals under the heading of calamine -- a zinc carbonate and a zinc silicate, which often closely resembled each other. The zinc carbonate was later named smithsonite in honor of Smithson, while the zinc silicate was named hemimorphite. The name calamine is no longer in use in mineralogy; now it is used only for the pink mixture known as "calamine lotion," which contains zinc oxide and iron oxide.
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| Hemimorphite Rough Stone |
James Smithson was not only a important scientist, he was also a shrewd investor who amassed a fortune during his lifetime. Though he had never visited the United States, his will stipulated that his wealth should go "to the United States of America, to found at Washington, an establishment for the increase and diffusion of knowledge among men." In 1846 the Smithsonian Institution was founded with Smithson's fortune.
Blue Hemimorphite from Congo |
The zinc silicate hemimorphite is rarer than the zinc carbonate smithsonite. The name hemimorphite derives from the unusual character of its crystals: the crystals are terminated by dissimilar faces. One end of the crystal is rather blunt being dominated by a pedion face while the opposite end is terminated by the point of a pyramid.
Hemimorphite is an important ore of zinc, since the mineral contains over 50% zinc. Gem-quality hemimorphite is usually blue or green, and bears some similarities to chrysocolla, smithsonite and turquoise. In an aggregate form, hemimorphite often displays bands of blue and white, or is mixed with a dark matrix.
Gemologically, hemimorphite has a refractive index of 1.614 to 1.636 and a density of 3.30 to 3.50. It has a hardness of 5 on the Mohs scale with perfect cleavage.
Hemimorphite deposits are found in Australia, Algeria, Mexico, Namibia, the Congo, Austria, Italy and the United States. |
