Hambergyle

Hambergyle, also known as hambergite, was a somewhat rare semi-precious stone.

Description
Hambergyle was found in crystal or fragmentary form. It was colorless and fairly hard, yielding small, faceted gems. A typical specimen had a base value of 50 gp.

Powers
If a hambergyle gem was held in a flame and light was cast upon it, the gem was consumed but produced a continual light at that spot.