Chrysoprase

Chrysoprase, also known as stormrock, was a translucent chalcedony with an apple-green color.

Description
This semi-precious stone was found throughout the Realms but its greatest concentration was in the Stormhorn Mountains of Cormyr. Chrysoprase was used in the creation of items which provided invisibility and was used to ornament rings of invisibility. A typical stone had a base value of 50 gp.