Starstone

Starstone is found in the deepest parts of the earth and has only been recovered a handful of times during dwarven mining expeditions. It is a clear rock, but it looks as though someone put the stars and nebulas of the sky into the rock, which in turn gives way to a faint glow. Working with starstone is near-impossible, as the slightest mistake or wrong chip can cause the flecks of apparent stars to disappear in an instant. The most famous starstone sits in the crown of the leader of the Dwarven Holds, though many other kings and queens have had smaller pieces adorning their royal wear.