Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel. Its colour is normally apple-green, but varies to deep green. Unlike emerald which owes its green colour to the presence of chromium, the colour of chrysoprase is due to trace amounts of nickel compounds in the form of very small inclusions.
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. The image on right shows the polished stone..