Alexandrite

Alexandrite was a greenish variety of chrysoberyl that appeared reddish under non-natural light, such as light spells. This transparent gem was usually faceted and used in pendants and earrings. Alexandrites were used as a magic focus for items that provided good luck, favorable reactions, protection, or other good omens. Examples included luckstones and the cursed lodestone. A typical specimen had a base value of 100 gp or 500 gp.