Chrysoprase

Derivation: From "chrysos prason" (Greek) gold leek

Description: Bright opaque and green.

Chrysoprase is a vivid green. It's obvious why it's named after a leek, but not as obvious why it's named after gold, unless it's to describe the way it almost glows.

Another name for chrysoprase is plasma (mentioned in "Kim" by Rudyard Kipling). This comes from "plasma" (Greek) meaning a thing molded.