Sheen

Sheen was a variety of obsidian which had many minute, spangly inclusions ranging in color from mahogany to silver and gold (the most valuable of these, gold sheen, was a semi-precious stone).

Description
This ornamental stone was usually tumbled (if large and attractive) or cut cabochon, and could be polished to a glossy, gleaming finish. A typical stone had a base value of 10 gp.