This is a beautiful, sky-blue hemimorphite specimen from the old 79 Mine in Arizona, USA. It has a beautiful sky-blue coloration and formed as a botryoidal lining within small rock cavities. While this area still has some active claims that are occasionally mined, most of the specimens collected now are aurichalcite and smithsonite. This hemimorphite specimen was acquired from an old collection and is still in excellent condition.
Hemimorphite is a basic hydrous zinc silicate with the chemical composition Zn4Si2O7(OH)2 · H2O. It earned its name from the structure of which the crystals form, through greek terminology. It has two different terminations on each side of the crystal, hence the inclusion of the greek terms "hemi", meaning half and "morph", meaning shape. The crystal formations can range anywhere between a crystal druze or botryoidal formation, to radiating acicular crystals, and more. The color of these crystals have been found to be white, beige, light brown and blue. On rare occasions, yellow and green crystals have been found.
Prior to 1803, hemimorphite and smithsonite were thought to be the same mineral called "calamine". However, following further scientific research, it was concluded that these were two distinct minerals.