Superior Swirl Slag, Sterling Silver Necklace

I just purchased a few slabs of this very unique glass. It's call Superior Swirl Slag, and is found in Lake Superior in the upper peninsula of Michigan. This slag was made during the 1850's to 1870's and is traced to many of the furnaces that were once in operation near or along Lake Superior. It is technically a glassy slag left from a copper smelting mining process. As is typical of this glass, this cabochon shows a couple pinhead sized pits, which does not affect the aesthetics of the piece.

I've cut out disc shapes on the back to let the color and slight bit of light through.

The pendant itself hangs 2" from the chain, and is 7/8" at the widest. (50mm x 21mm) The sterling silver chain is 18" long and finished with a sterling lobster clasp.

The metal has been oxidized and then sanded to a satin finish.