Opal

Opal contains up to 20% water trapped in its silica structure. Because opal has the colors of other gems, the Romans thought it was the most precious and powerful of all. When Australia’s mines began to produce opals commercially in the 1890’s, it quickly became the world’s primary source for this October birthstone. Five of the main types of opals are; White or Light opal, Black opal, Fire opal, Boulder opal, and Chrystal opal. Play of color occurs in precious opal because it’s made up of sub-microscopic spheres stacked in a grid-like pattern. As the lightwaves travel between the spheres, the waves diffract, or bend. As they bend, they break up into the colors of the rainbow, called spectral colors, resulting in play-of-color. Opal can range from 5-6.5 on the Mohs hardness scale.