Boulder opals have been growing in popularity over the years and many customers approach me with questions about these amazing stones. I enjoy talking to people about opals and so I've developed a few commonly asked questions to help our readers better understand these amazing opal gemstones.
What makes an opal a "Boulder Opal"?
Sometimes people think the name 'boulder opal' means these opals are more rock like or that they don't have the 
same rainbow coloring as other opals. But don't let the name fool you. Boulder opals are actually one of the most valuable types of opal, second only to the well-known and internationally respected black opal. The hallmark of a boulder opal is the layer of ironstone left on the back of the stone. Ironstone, as its name implies, is an incredibly hard type of rock. The veins that create boulder opals are extremely thin and somewhat fragile from a mining perspective so that is why the ironstone is left on the back. But that does not mean the brilliance or color is diminished in these stones. Quite the contrary, the spectrum of colors on display in a boulder opal are simply amazing.
The dark backing of ironstone on these opals create a darker tone for the overall body of the opal. This makes the colors displayed on boulder opals even more vibrant and stunning, much like the effect the darker undertones have on black opals. There are times when the ironstone appears in spots on the front of a boulder opal. Many clients like this mottled look as it offsets the colors of the opal. Nevertheless, while mottles boulder opals are popular, a boulder opal with a whole bar of color is on display - referred to as being 'clean faced' - is more valuable and highly sought after.
What Is the Value of a Boulder Opal?
As with any precious gemstone, values fluctuate based on a number of factors. The market itself, of course, plays a part as does the quality and size of the stone itself. Finally, how it was mined, clean, shaped and polished all contribute to its final valuation. But, in terms of a ballpark figure, a truly top shelf example of a boulder opal has been known to command as much as AUD 3,000 per carat. This is, of course, the very top end of the spectrum but it gives you some idea as to how well regarded and valuable these particular opals are.
Where Do Boulder Opals Come From?
Boulder opals are only found in a certain part of Australia. They are mined in the Queensland area with opal fields in Quilpie and Winton. Obviously, their geographic specificity also adds to their overall value.
Boulder opals are a popular investment for people who want to grow their gemstone and opal jewelry collection. They offer a literal slice of beauty provided directly from the Earth. In the end, boulder opals are truly powerful - both in their beauty and in what they represent in terms of the beauty our planet can create.