Opal is an extremely precious gem.
Opalsare in a class by themselves. As a species, opal is so unique that it has its own descriptive vocabulary. More than any other gem, each opal is distinctly individual.
Opals are also the most delicate gemstones that are commonly used and require special care. It is generally accepted that the dominant background color is often the way in which the stone is identified. Black opals, such as those in Lightning Ridge, are generally considered to be the most valuable because the rest of the vibrant colors in the spectrum and their patterns are best seen with the black background. The patterns seen on opals can resemble stained glass windows, butterflies, birds, and other natural and artificial shapes.
Dramatic variation in color and types of color play phenomena make opal a hard gemstone for determining value. The term crystal opal refers to the 'diaphanity' (transparency) of an opal, not its crystal structure, and is defined as any type of opal that is translucent to transparent. Since opals grow by filling cavities in the earth, they sometimes take the form of pieces of wood, bone, and seashells buried in the ground. Hays and his partner say they are selling the collection now because the market for colored gems in general and opals in particular is strong.
The thickness of the opal color bar is relative to the overall size and shape of the individual stone. The best opals are black background color with a colorful, bright and evenly distributed play of color, free of any treatment and of Australian origin. In some cases, the natural shape of the pieces or the color inspired the name of the opal, such as “The Pharaoh”, “The Parrot Fish” and “The Blue Lagoon”. Body tone refers to the background or “underlying color” of opal, ranging from black to dark to light.
Magnificent but highly hydrated, this opal has a strong tendency to crack due to water loss when exposed to air. Therefore, the most valuable black opal of all is a very bright red stone on a very black base that simply shines. Opals are not recommended for ring stones, unless the stone is placed in a protective setting or triplet or is reserved for occasional use. Slowly, over time, minerals from the depths of the earth came to the surface and grew in the cavities of the bedrock to form opal.
Colorless and transparent to semi-transparent in transmitted light, glass opals have a rich play of colors in reflected light. The particular colors seen in the fire of an opal depend on the size of the spheres and the angle of view.