The novel's heroine owned an opal that burned fiery red when she was angry and turned ashen gray upon her death. Queen Victoria finally dispelled the curse by giving opal jewelry as gifts at a royal wedding. The physical structure of opal is unique. Tiny spheres of silicon dioxide form a pyramid shaped grid interspersed with water. The effect is similar to the rainbow colors displayed on a soap bubble, only much more dramatic.
Opals vary widely in body color, with white the most common.
Black is considered the most valuable as it enhances and accentuates the play of color. Green and blue opals are rare. Opal is sometimes cut with pieces of matrix - the host rock. This strengthens the opal and can also lend a more interesting appearance. Their unusual shapes and ironstone inclusions make Boulders popular with progressive, modern designers and wearers and are most popular as Opal brooches.