Jevonite
Jevonite was a rare mineral  said to be "breathtaking" in appearance. The First Hebitian civilization of Cardassia Prime produced magnificent artifacts made from jevonite; however, most of the artifacts were plundered by impoverished Cardassians. 

Gul Madred owned a dagger with an ornate handle made of this stone. When he showed it to Jean-Luc Picard in 2369, he felt sure Picard would understand why the mineral was so prized. ()

In the 2370s, the Ferengi Alliance was purchasing as much jevonite they could find. In 2373, Grand Nagus Zek explained to the Board of Liquidators why he was insisting they do so. ()

External link 
 

de:Jevonit
nl:Jevonite
Gemstones