The crystal or white opal is a variety of opals known for their transparency and color play.Light passes easily through the surface and in the heart of the opal, which gives it an iridescent color. The crystal opals, like all opals, are composed of hydrated and non-crystalline silica. Due to their amorphous sturcture, opals are not minerals but mineraloids as well as substances such as amber, coal and obsidian. The chemical formula of the opal is SIO2.nH2O .

With their amorphous structure, these opals can show a superb set of colors. The classification of their color involves looking at the background color and the iridescence game inside

White opals, which are precious stones containing water and having coloured reflections. White opals are formed by the accumulation of siliceous fluids from different rocks. They originate in Australia, Brazil, Guatemala, Honduras, Japan, Mexico, Peru and the United States. White opals have lithotherapy virtues, such as heart humidification, protection against aquatic accidents, aura purification and stimulation of creativity. Here are some raw opals from Coober Pedy in Australia