OPAL consists of submicroscopic silica (a compound of silicon and oxygen) spheres bonded together with water and additional silica.
It is the product of seasonal rains that drenched dry ground in regions such as Australia’s semi-desert “outback.” The showers soaked deep into underground rock, carrying dissolved silica downward, which evaporated during dry periods, leaving solid deposits of silica in the cracks and between the layers of underground sedimentary rock. These silica deposits formed opal.
Opal is known for its unique display of flashing rainbow colors called play-of-color. This phenomenon occurs in precious opal because it’s made up of sub-microscopic spheres stacked in a grid-like pattern, and as the lightwaves travel between the spheres, the waves bend breaking up into the different colors of the rainbow. The color you see varies with the sizes of the spheres. Spheres that are approximately 0.1 micron (one ten-millionth of a meter) in diameter produce violet. Spheres about 0.2 microns in size produce red. Sizes in between produce the remaining colors.
Many types of opals are found across the world
Australian Boulder Opal, in which fragments of the surrounding rock, called matrix, become part of the finished gem.
Crystal or water opal, such as Ethiopian welo opal, which has a higher concentration in water (making the stone more unstable and prone to drying and cracking) but displays exceptional play-of-color.
Fire opal's color can range from brown, yellow, orange, or red, and often doesn’t show play-of-color—It comes from Mexico and is also known as Mexican opal or Cantera opal.
Our gold-plated pieces feature Gilson opal, a man made opal grown in a laboratory from opaline silica (mimicking all the properties of natural opal) in a 14-18 month process. Its low water content makes Gilson opals much stronger and capable to withstand high temperatures without cracking.