Cowell Jade History
Jade Deposits near Cowell on the Eyre Peninsula (South Australia) are among the largest nephrite jade deposits in the world. They were discovered in 1965 when Harry Schiller, a local farmer prospecting in the area, collected a 3-4 kg boulder of dense, hard rock near an outcrop of white, marble. The boulder was tested and identified by Adelaide University and the South Australian Museum.
91 separate jade outcrops were identified by the SA Department of Mines geologists in 1974, today well over 100 outcrops are known. All outcrops are located within an area referred to as the Cowell Jaded Province. All these sites occur on 23 leases held by Gemstones Australia Pty Ltd.
Techincal infromation about the Cowell Jade product
The Jade bodies at Cowell typically have elongated, lensiod shapes in outcrops. Host rocks are dolomitic marble and banded calc-silicate of the Palaeo to Mesoproterozioc Minbrie Genseiss, These high grade Jade deposits were form some 1840 million years ago.
Cowell Nephrite formed:
- Within alteration zones as large boluders up to 40m long by 3m wide
- Within cross-fractures up to 1m wide parallel to the axial plane during late-stage cross warping. Nephrite in cross-fractures is typically HIGH QUALITY, FINE GRAINED, MASSIVE AND DARK GREEN TO BLACK, but does occur in raer translucent light green colours
- Withing irregular alteration of course-grained, brecciated diopside, producing schistose nephrite that has diopside inclusions
The geological setting at Cowell host rocks differs with other major occurances of nephrite in New Zealnd, Canada and Taiwan, where lenses occur within or along the faulted margins of serpentised ultramafic rocks such as peridotes. With gives COWELL JADE, its fine grained and consistent dark rich green and black colours.
Cowell Jade exhibits a variety of colours and textures, but consists mainly of medium to fine grained material greenish to solid black hues.
The 3 main varities are marked:
- Green Nephrite
- Black Nephrite
- Premium Black Nephrite
All products become a very high polish finish, with simple lapidry techniques, with the Very fine-grained premium black obtaining a mirror like polish.