chrysoprase

One of the rarest of the chalcedonies,chrysoprase is considered to be the most valuable. A lot of commercial chrysoprase ischalcedony artificially stained by impregnation with a green salt of nickel. Known to fade in prolonged exposure to sun, chrysoprase's resulting colorcan easily be confused with or passed off as fine jade.  Nickel Mountain was the last operatingmetal mine in Oregon, due to declining worldwide nickel prices through the1990�s.  Mined largely by hand, thin layers of the saprolite clay in which it is found arestripped away by bulldozers or other heavy equipment, after which thegemstone itself is collected by hand toprevent damage.  In 1991, at the International Gemological Symposium, Brisbane gemologist Grahame Brown estimated that Australiahas sufficient deposits to supply the world for another 20-40 years.

golden leek or granny smith? carved chrysoprase koalas photo: gem exotica Although its Greek name meaning "golden leek," denotes a golden yellow color, chryoprase is actually a beautiful translucent apple-green color, similar to Granny Smith apples. Formed by the weatherization of serpentine, chrysoprase occurs as fillings in cavities in serpentine. As the elements break down the serpentine, nickel, silica and other iron oxides are dissolved out of the stone and collect in cracks, crevices and saprolite (a soft, rich clay) in the underlying environment. chrysoprase mine, marlborough, queensland Australia currently has the worlds largest deposits of quality chrysoprase, estimated to be about 85% of world supply; it also has a pale lime variety known aslemon chrysoprase. Deposits are found in the Marlborough district of central Queensland, at Mount Davies in the remote northwest of South Australia, and at Wingelina and Yerilla in Western Australia. Queensland's chrysoprase is the most water-retentive, and therefore, the least prone to color fade or cracking. The gem is also found to a limited extent at Revdinsk, near Ekaterinburg, in the Russian Urals, as well as in India. The US has several locations -- most notably at Nickel Mountain, near the small town of Riddle in Douglas County, Oregon (in the southwest part of the state) -- where it occurs in nickeliferous serpentine.