Kevas were commonly traded goods among merchants during the 23rd and 24th centuries.
Spock posed as a trader of kevas and trillium while on Organia. Arne Darvin did the same while aboard the USS Defiant. (TOS: "Errand of Mercy"; DS9: "Trials and Tribble-ations")
In the first draft script of TOS: "The City on the Edge of Forever", keva was established as a kind of Vulcan food which contained purple juice.
The Star Trek Encyclopedia, 4th ed., vol. 1, p. 414 described them as gemstones.
External link
- Keva at Memory Beta, the wiki for licensed Star Trek works