Precious opal is known for its remarkable ability to diffract light, which results in rainbow-like colors that change with the angle of observation - known as 'play of color'. Fire opal can sometimes exhibit slight color play, but it is better known for its vivid body color. Common opal is usually opaque, rarely translucent, and lacks play of color.
Opal can occur in many colors including white, colorless, pale yellow, pale red, gray, brown and black. Diffraction can cause flashes of any color of the rainbow which can be seen in opal's color play. Yellow, blue and green are most common, whereas violet, red and orange are the rarest colors seen through play of color.
Opals are usually cut into shapes which maximize and preserve the weight of the rough opal. They are often cut en cabochon and depending on the opal color bar, it may be cut with low or high domes in order to maximize play of color and adularescence. Opal can also be faceted, most often seen with 'fire opal'.