Ophealine

Ophealine was the name in the Realms for axinite, also called "glass stone" or, if violet in hue, yanolite.

Description
These ornamental stones were commonly brown in color--such a vivid brown that large crystals appeared almost opaque. Ophealine was cut in facets, and although not possessing one of the most attractive gemstone hues, it could yield finished gemstones of considerable size, both hard and durable. On the streets of Waterdeep, such gems were once known as "knuckle stones"; when polished and mounted on rings, their sharp edges laid open many a noble's or thief's face at many a drunken party. A typical stone had a base value of 10 gp.