Chalcedony

Chalcedony was a semi-precious stone that was the base mineral in many gem-quality stones, but in the Realms the more colorful varieties all had their own names (see below). In Faerûn, chalcedony referred to the mostly colorless versions of these gemstones.

Description
The vast majority of chalcedony gems were white to off-white, rarely shading to gray or black. They could be found in deposits that yielded large gem-quality stones that could be carved into statuettes or coffers. Smaller stones were typically cut cabochon and polished, often giving them a resemblance to ivory. A typical stone had a base value of 50 gp.

Varieties
Chalcedony took on a wide variety of colors, each with their own unique properties:
 * Agate: the entire family of agates that spanned the rainbow
 * Bloodstone: green-gray with red inclusions
 * Carnelian: red to reddish brown
 * Chrysocolla: green to blue-green
 * Chrysoprase: light apple-green
 * Crown of silver: metallic silver with black bands

Powers
This stone was used in the creation of magic items that conferred protection from the undead or control over them. For necromantic purposes, this gem could be used instead of human bone, improving the efficacy of items dealing with nonhuman undead.

Crushed to a powder and enchanted with an easy spell, chalcedony added to an alcoholic beverage prevented intoxication without altering the taste of the drink, making it a favorite of agents and spies that needed to keep their wits sharp.