Opal

Opal is a milky gemstone that diffracts light into many colors. The stone is usually pale blue with green and gold splotches, but other colors are not uncommon. In the Realms, this variety was slightly more common than fire opals and black opals and were the primary type of opal used as a material component in casting spells and creating magic items such the helm of brilliance. In non-magical use, opals were typically cut cabochon or used as inlays. A typical specimen had a base value of 1000 gp.