Opal
Opal is the product of seasonal rains that drenched the ground in dry 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 can be classified into two categories, common opal and precious opal, however when most people think of opal they exclusively refer to precious opal, which is known for its unique display of flashing rainbow colors called play-of-color.
This effect is caused by the refraction of the light traveling between the sub-microscopic spheres that compose this beautiful rock. 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.
As far back as 4,000 BCE, humans have treasured opals and mined them in various locations, such as Kenya and Hungary. However, nowadays, Australia has 95% of the world’s supply of commercial opal and the largest percentage still comes from the 70 opal fields around Coober Pedy, a mining town in the Australian outback that is often compared to the moon for its lunar-like landscape and where locals prefer to live underground in dugouts where it is cool in summer and warm in winter.
Gilson opal, a type of opal characterized by a base tone ranging from colorless to medium gray and pastel play of color featuring small flashes of yellows, oranges, pinks and blues. This type of opal is grown in a laboratory from opaline silica in a yearlong process using the same chemical composition as natural opal but without water. This slow growth helps to make stronger, more durable opals with the same intensity of color as natural specimens.
We use Gilson Opals for all our pieces, as they are beautifully colored and stable enough to withstand gold-plating without damage.