Zircon

Zircon was a mineral that could be cut into faceted gems.

Description
Zircon was volcanic in origin, found in igneous rock formations. It was a brownish crystal that turned pale blue when heated sufficiently and could be cut into faceted gemstones. Zircons were sometimes substituted for more valuable gems to fool the uninitiated, but anyone with a passing knowledge of gemology (a jeweler, a dwarf, or even a seasoned adventurer) could notice the difference. Zircons had an affinity for magic and could be enchanted easily, making them a favorite for use in creating magical items. A typical specimen had a base value of 50 gp.