Hemimorphite: Properties, Facts and Photos
What is Hemimorphite?
Hemimorphite is a zinc silicate, a chemical compound of zinc, silicon, oxygen and hydrogen. It was once believed to be the same mineral as Smithsonite, which is a zinc carbonate. Zinc carbonate is a compound of zinc, carbon and oxygen atoms.
The confusion was caused by the similarity of the two minerals' external appearance. Until the early 1800s, both were known as 'calamine'.
The British chemist and mineralogist James Smithson then discovered, from a chemical and crystallographic perspective, that they were two distinct minerals.
The zinc carbonate was later renamed Smithsonite after James Smithson.
The name 'Hemimorphite' came from the Greek words 'hēmi', meaning 'half', and 'morphē', meaning 'form', in reference to the stone's hemimorphism. A mineral that's hemimorphic has a different crystal habit at opposite ends of the same crystal.
Roman author, naturalist and natural philosopher Pliny the Elder wrote about hemimorphite and referred to it as 'galmei'. Other ancient writers referred to it as cadmia, which is an oxide of zinc.
The name 'calamine' came from the corrupted Greek word cadmia. German geologist and mineralogist Gustav Kenngott [1818-1897] renamed it hemimorphite, albeit unofficially.
American clergyman and mineral dealer Ebenezer Seymour described hemimorphite in 1868 following studies of samples from Romania. The obsolete name 'calamine' remained in use until the 1930s.
Hemimorphite Physical Properties
Hemimorphite is moderately hard and brittle, with a maze of hairline fractures. These characteristics make it extremely difficult to cut. For this reason, when used as a gemstone, it tends to be polished as a cabochon.
Blue hemimorphite can resemble turquoise or is sometimes mistaken for larimar. In China, it's often sold as 'Chinese larimar'. There are many cases where people have bought larimar from China only to discover it's hemimorphite.
Although white or colourless in its purest form, hemimorphite can look blue, green or grey due to impurities of copper or iron.
Hemimorphite, which grades 4.5 to 5 on the Mohs scale of hardness, is known to occasionally fluoresce blue under shortwave ultraviolet light.
It can be found in several countries around the world, including on the Belgian-German border, Poland, the USA, North Africa, Thailand, Sardinia, Siberia, Austria, Namibia, Spain, Australia and England.
Some of the finest material, which includes colourless and transparent gemmy crystals, come from Mexico.
Article Pictures
Our hemimorphite photos are courtesy of Ron Wolf.
Pop-up photo
Smithsonite: Courtesy of Stan Celestian.
