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 19.5 mm x 15 mm, is 5 mm thick, and weighs about 10.4 carats. It is cabochon cut and may not fit into a standard jewelry mounting but would be beautiful if custom wire-wrapped! Shipped USPS Priority. SO-02.