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 13 mm x 12 mm, is 2.5 mm thick, and weighs about 3.6 carats. It is cabochon cut and MAY fit into a standard jewelry mounting but would also be beautiful for a custom piece! Ships USPS Priority Mail. SO-07.