Introduction
Have you seen the gemstone in which patches and seams of opal are present that are surrounded by natural host rock? Well, this particular stone is known as Boulder Opal. Also known as “Natural Opal Type 2,” jewelers use an inventive cutting style where the small patches and seams are cut with the host rock. The reason why they do not cut only solid opal areas (by isolating them) is because the opal areas are too small to cut. In this blog, we are going to talk about Boulder Opal rings, where we will explain the colors and patterns that you should look for in a Boulder Opal ring, and we will also understand why these rings command higher value. So, let us begin by first going into the specifics of this gemstone.
What is Boulder Opal?
As a beautiful semi-precious gemstone, the Boulder Opal is a variety of precious opals that are found only in Western Queensland, Australia. These opals exist within sandstone or ironstone host rock, and when you look at a slice of this gemstone, you find an awesome contrast between the glimmering opal and earthy tones of the ironstone/sandstone matrix. The two most popular mining areas of Boulder Opal are the Yowah Mining Area (which is located halfway between Thargomindah and Cunnamulla) and the Koroit Opal Mining Field.
Mineral Composition of Boulder Opal
Primarily composed of hydrated silica, this gemstone has the chemical formula of SiO2.nH2O. The water content within Boulder Opal varies from specimen to specimen. Typically, water content ranges from 3% to 21% by weight, however, if we make generalizations, then we can say that it ranges between 6% to 10%. Other elements present in this gemstone include:
- Iron Oxide (Fe2O3)
- Aluminum Oxide (Al2O3)
- Trace elements such as copper, nickel, manganese, etc.
Physical Properties of Boulder Opal
- Hardness: Ranges between 5.5 and 6.5 on the Mohs Scale.
- Specific Gravity: Varies from specimen to specimen, ranging from 1.98 to 2.25 – the variation is due to differences in water content.
- Luster: Can vary from waxy and resinous to vitreous.
- Transparency: Most of the time, opaque (because of ironstone backing).
- Fracture: Conchoidal fracture, similar to other opal varieties.
- Tenacity: Brittle
- Refractive Index: 1.370 to 1.470
- Optical Character: Isotropic
- Structure: Amorphous or non-crystalline structure composed of tiny silica spheres arranged in a three-dimensional lattice.
Why Do Boulder Opal Rings Command a Higher Value?
There are several reasons why Boulder Opal rings are the second most valuable opal rings, next to black opal rings, some of which are:
Durability and Strength of Boulder Opal Gemstone
All Boulder Opals possess a natural ironstone backing, which provides them extra strength and hardness. This is why boulder opal rings are considered more resistant to impacts and occasional knocks than other opal rings, and this factor also improves the perceived value of these gemstone rings.
Mineralogically, Boulder Opals form within ironstone or sandstone boulders, which is why they possess a unique structure in which the opal is attached to its host rock. When the stone is cut in cabochons or freeform shapes for use in jewelry making, it is given a natural ironstone backing. This backing acts as a protective layer that shields the complete gemstone from accidental damage. In other words, the ironstone matrix creates a sturdy base for the Boulder opal gemstone, and when any impact happens, the forces are distributed more evenly, which is why there is very little risk of cracks or chips.
Unique Appearance
Because of the strong contrast between the vibrant opal showing the play of colors and earthy tones of the ironstone matrix, the color display is significantly enhanced. Also, many times, the natural ironstone backing ends up creating stunning visual effects, such as that of landscapes or cosmic scenery. This unique appearance of this stone results in the Boulder Opal jewelry being priced significantly higher than other opal varieties.
Rarity and Origin
Boulder Opals are found only in one place in the whole world, which is Queensland, Australia. This contributes to the rarity of this opal variety. Also, the mining conditions are quite challenging, especially in remote areas of Queensland, which is why the Boulder Opal rings are rarer in comparison to other opal rings.
Market Demand
As more and more people got to know about Boulder Opals, there was a surge in the demand for this opal variety. The surge in demand could not keep up with the supply of this gemstone, and this was why the prices of Boulder Opal rings (and other jewelry) increased in a short span of time.
It’s interesting to note that since the gemstone jewelry manufacturers could get enough supply of Boulder Opals, they started using the specimens in irregular shapes (which are basically freeform shapes) with fancy cuts. It has been seen that a lot of stone gets wasted when this opal variety is cut in cabochon, and in order to reduce stone wastage, jewelers cut this stone in fancy cuts. This innovative way is used by many jewelers and jewelry manufacturers to cope with the limited supply of Boulder Opal.
Colors and Patterns to Look for In Boulder Opal Rings
Colors to Look for in a Boulder Opal Ring
You can see a wide range of colors in a Boulder Opal ring. Blues and greens, although common, are highly desirable. Reds and oranges within the ring are often considered to be more valuable because of their rarity. Purples and yellows can also be present, and although they are extremely hard to find, very few people have a taste for these colors, which is why they are not in demand. Also, while buying this gemstone ring, you need to ensure that it has multiple colors with a strong contrast, with the presence of detailed, saturated hues. Last but not least, just make sure that you get a dark background of ironstone, so the color intensity looks enhanced.
Patterns and Textures to Consider for Your Boulder Opal Ring
Some of the desirable patterns within a Boulder Opal ring that you should look for are:
- Areas with broad flashes of sweeping patterns, which are basically large areas that change color dramatically when light hits them at different angles.
- Although less desirable, you can look for areas with pinfires, which are small, closely spaced patches of color within the ring.
- Though rare in Boulder Opal, you can look for harlequin patterns, which are large, angular patches of color.
- One of the most well-admired patterns is those of Chinese writings, which are basically intricate, script-like patterns.
- You can also look for stripes and bands of colors, which are known as the signature ribbon patterns within Boulder Opals.
- Ensure that within the Boulder Opal ring, patterns are evenly distributed, and they cover a considerable portion of the stone set in the ring.
Unique textures that you can look out for within the gemstone ring are:
- Veined patterns, where you see waves and veins shining with the colors of opal that run through the stone.
- Natural ironstone backing, giving the ring an earthy and adding character to the ring.
- Undulating or freeform shapes that mark the natural origins of the opal.
Conclusion
So, this is it, peeps – we have discussed everything about Boulder Opal rings! Now that you are fully aware of which colors and patterns you need to choose in a Boulder Opal ring, you can confidently go to the jeweler and buy one such ring for yourself.
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