Slocum Opal is a man-made Opal that was developed in the 1970’s by John Slocum of Rochester, Michigan. His creations were among the first Opal simulants available on the market. He used a secret process that was lost when he died. It is harder and more durable than natural Opal, and each pretty stone is different. We do have a selection of other pieces as well, but this is old stock, never to be produced again! This piece measures approximately 32 mm x 16 mm, is 6 mm thick, and weighs about 23.2 carats. This is one of the largest pieces of this material that we have! It is cabochon cut and probably would not fit into a standard jewelry mounting but would be beautiful for a custom piece! Ships USPS Priority Mail. SO-08.