Oval Obsidian stud earrings in sterling silver.
Obsidian is formed when lava extruded from a volcano rapidly cools. It is a naturally occurring volcanic glass.
A cabochon (from Middle French) is a gemstone which has been shaped and polished as opposed to being faceted. The resulting form is usually a convex (rounded) obverse with a flat reverse. Cabochon was the default method of preparing gemstones before gemstone cutting was developed.