Opal is a unique gemstone, exhibiting a characteristic display of spectral colours caused by diffracted light eminating from within the gem.

Australia is the world's leading producer of precius opal. Black opal 'nobbies' are produced at the Lightning Ridge field in the central north of New South Wales.

The black opal is found in sedimentary rocks that were deposited in a freshwater environment during the Cretaceous period, about 110 million years ago.

Opal is currently being mined from depths between 3 feet and 90 feet below the surface.

Black opal ranges in price from $A50.00 per piece to as much as $3,000 per carat.