Crystal Kobolds use crystals to mine more crystals to trade for bigger, better crystals and trinkets. Like other kobolds these guys are greedy, and their primitive societies typically produce industrious and resourceful individuals. Crystal kobolds are also a little smarter than your standard kobold, but with higher intelligence just comes a greater capacity for evil.
Tourmaline the Crystal Kobold always has dirty feet and hands with busted knuckles. She comes to town in the evenings to down a pint and make a trade or two, but is hardly above any sort of side quest for another bag of gems.