Opal facts:

• The word opal is adapted from the Roman term opalus.
• It is suggested it was adapted it from Ops, the wife of Saturn and goddess of fertility. The portion of Saturnalia devoted to Ops was “Opalia”, similar to opalus.
• Opal is a form of silica related to quartz, not a mineral
• Opal’s internal structure makes it diffract  light; depending on the conditions in which it formed it can take on many colors. Opal ranges from clear through white, gray, red, orange, yellow, green, blue, magenta, rose, pink, slate, olive, brown, and black. Of these hues, the reds against black are the most rare, whereas white and greens are the most common
• The lattice of spheres of opal that cause the interference with light are several hundred times larger than the fundamental structure of crystalline silica. As a mineraloid, there is no unit cell that describes the structure of opal.
• In the Middle Ages, opal was considered a stone that could provide great luck because it was believed to possess all the virtues of each gemstone whose color was represented in the color spectrum of the opal
• Birthstone for the zodiac sign libra.