Learn more about boulder Opal!
What is boulder opal, and what is its significance in the world of jewelry? One of the best and often beloved gemstones among people is OPAL. Whether they are pendants or stone opal rings, they seem to be the focus of their beauty, but they also receive many questions from collectors. What is stone opal? And why isn’t it just called Opal?
Boulder opal is a boulder that contains delicate veins and patches of opal that are surrounded or attached to their natural host boulder. A tailor studies this stone and decides how to cut the stone as best as possible. This stone can be cut to reveal valuable opal seams and spots as they appear in its natural host boulder. Alternatively, the gemstone can be cut to have a thin seam of gemstone opal as the surface of the stone and its natural host boulder as the base.
Some people also consider “stone opal” to be the original cutting style in which the delicate stitches and gemstones of opal that are too small to be cut into hard opal gems are used extensively. It is also known as Type 2 Natural Opal.
Boulder opal is a type of opal that is always attached to the host boulder, usually ironstone or petrified sandstone. When boulder opal is formed, silica-containing water seeps through the cracks and forms opal. If the silica balls are correctly aligned, you will get valuable opal or opal with a play of colors. The size of the silica determines the bursts of color you see. The little balls give you blue, and then you climb the rainbow to the giant red ball. Opal refracts light instead of reflecting it like most other gemstones. Light entering the gem envelops the silicon sphere and causes the light to break down into spectral colors.
It is impossible to remove this opal from the host boulder without damaging the opal, and the seams in the opal are usually so thin that they are not worth it. It is challenging to buy raw stones, you never know what is inside, and the risk is enormous.
Australian boulder opals are the second most crucial opal (after black opal). Boulder opals are easy to recognize by the hardened layer of brown ironstone that remains behind the rock. As the name suggests, stone opals are mined from sizeable underground iron boulders. Thin strips of colored opal in the cracks and crevices of these boulders. Because these stripes of color are skinny, opal cutters have to leave ironstone behind the opal to create a full-size stone. A thin layer of opal in stone opal can display any spectrum color in a beautiful color scheme.
Although the ironstone layer that forms the basis of stone opals may appear like doublets at first glance, the formation is quite natural.
Due to the iron stone’s dark base, stone opals usually have a dark body tone, resulting in a light color similar to that of black opals. Sometimes ironstone is visible on the rock’s surface, giving it a colorful or spotty appearance and reducing the stone’s value. Stone opal with a “clean face” where a whole band of color is visible on the stone’s surface is much more desirable and valuable than ironstone’s tinted cover.
The subtlety of the ribbon in stone opals means that surfaces with tall cabochons are extremely rare. Stone opals usually have a flat or wavy texture. For this reason, stone opals are almost always cut free to maximize the size of the stone.
Stone opal matrix
There are several types in the bouldering world. The first is the boulder opal matrix. This material contains a large amount of ironstone visible with opal stitching in the gemstone’s front view.
Corte stone opal
The second is koro, and I think it’s better to pronounce it with an Australian accent! This material looks like an opal bond between contrasting colors of Eisenstein.
Full face boulder opal
Finally, we have the full face boulder opal, where the opal covers the gemstone’s entire surface. This type of boulder opal is usually the most expensive globally and can rival the best black or helo opal.
The carat rating for stone opal is not widely accepted due to no small amount of ironstone. However, without them, high-quality stone opal can roughly speak, be very expensive per carat of a gemstone. A clean face stone with no iron stone stains is generally more costly than tinted stone. Find out more about opal prices.
