Also one of the rewards you can obtain from completing all 37 waves in TzHaar Fight Kiln.
A possible reward for looting the Kingly implings.
Possible reward from menaphite gift offering.
Used as payment to enter and kill Gemstone dragons in the Gem Rock Cavern under Shilo Village.
Used to add charges to Gemstone Armor.
Used to add charges to Gemstone Armor. Each uncut onyx adds 100 charges.