Wednesday, March 31, 2010

April 2010 Mineral of the Month


Chrysoprase is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel which provide it with its apple green to deep green color. The darker varieties of chrysoprase are also referred to as prase. The word chrysoprase comes from the Greek chrysos meaning 'gold' and prason, meaning 'leek'. As with all forms of chalcedony, chrysoprase has a hardness of 6 - 7 on the Mohs hardness scale and a conchoidal fracture like flint. The best known sources of chrysoprase are Queensland, Western Australia, Germany, Poland, Russia, Arizona, California, and Brazil. The chrysoprase and Ni silicate ore deposit in Szklary, Lower Silesia, Poland, was probably the biggest European chrysoprase occurrence and possibly also the biggest in the world. Chrysoprase was used by the Greeks, Romans, and the Egyptians in jewelry and other ornamental objects and because of its semi-opaque green color; it is often mistaken for Imperial jadeite. One of the most valuable chalcedony gem stones, chrysoprase is prized for its color and rarity. The stone occurs in serpentine rocks and in weathered materials of nickel ore deposits as nodules or in veins within the host rock