Semi-precious stone (3)

I believe the answer is:
jet
(Other definitions for jet that I've seen before include "Black; spurt" , "Black variety of lignite, used for ornaments" , "Spurt; aircraft" , "Rush" , "Deep black" .)
I believe the answer is:
jet
(Other definitions for jet that I've seen before include "Black; spurt" , "Black variety of lignite, used for ornaments" , "Spurt; aircraft" , "Rush" , "Deep black" .)