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Demystifying Opal — What is Boulder Opal



One of my favorite gemstones is OPAL — so it comes as no surprise I often sell lots of opal pieces over on shopGemGossip. Recently, I sold out of the boulder opal pendants I posted, which gained a lot of attention for their beauty but also a lot of questions from collectors. What exactly is boulder opal? And why isn’t it just called opal?

I knew I could count on my friend and colleague Brecken Farnsworth of Parlé since they sell some of the best opals I’ve seen in my entire career. Take it away, Brecken…

My venture into the world of Opal began when I met my future husband, Jonathan. His family started their business as Opal miners turned Gem dealers turned Jewelry Manufacturers, but that is a story for another day. Needless to say, I was excited to be falling in love with someone who had an endless supply of my favorite gemstone and birthstone! I will never forget my first visit to his family’s office… my mind exploded with the amount and variety of opals that were available. At the time, and to my limited knowledge, I thought the only type of opal that existed was a milky light opal. I remember when I turned 17, my parents designed an opal ring for me. My mother took that ring back to our jeweler three times because the opal didn’t have enough fire in it!

Flash forward to today, we have now been happily married for 12 years, have four-year-old twin girls and are now running the business his family started, Parlé.  On that fateful first visit to Parlé, I remember Frank, Jonathan’s Dad, showing us a parcel of opal he had just purchased. I waited eagerly while the package was opened, and what I saw shocked me! I even shouted, “that’s not opal.” Well it was and is a gorgeous type of opal called Boulder Opal.


Boulder Opal

Boulder Opal is a type of opal that is still connected to its host rock, which is usually an iron stone or fossilized sandstone. During Boulder Opal formation, silica-rich water seeps into cracks and forms opal, when the silica spheres align perfectly you get precious opal or opal with play-of-color. The size of the silica determines the flashes of color that you see. The smaller spheres will give you blue and then you go all the way up the rainbow to the largest sphere, red. Opal actually breaks light instead of reflecting it like most other gemstones. Light entering in the gem wraps around the silica sphere and causes the light to break into spectral colors.

It is impossible to remove this opal from its host rock without damaging the opal and typically the seams of opal are so thin it would not be worth the effort. Buying rough boulder is hard, you never know what is on the inside and the risk is huge.


Seams in Boulder Opal Rough

Our cutters “Chase the fire.” It is a term we use that means following the seam of opal through the iron stone. For this reason, it’s typical to see boulder opal with undulating surfaces as the cutters follow crevasses filled with opal in the host rock. This gives you amazing organic shapes and bright colors because of the darker nature of iron stone. It is common to see Boulder Opal that exhibits iron stone patches on the surface of the gem like a beauty mark. I like to think of them like moles… you can have a mole that enhances your appearance like Cindy Crawford or you can have the opposite, something that detracts from the gem. But in the world of Opal, beauty is in the eye of the beholder!


Boulder Opal Matrix

In Boulder world, we have several types. First is Boulder Opal Matrix. This material has a lot of visible iron stone with seams of opal running through the face up view of the gemstone.


Koroite Boulder Opal

Second is Koroite, I feel it’s best pronounced with an Aussie accent! This material looks like a painting with opal weaving between contrasting colors of iron stone.


Full Faced Boulder Opal

Finally, we have full faced Boulder Opal, where opal is covering the entire face of the gemstone. This type of Boulder Opal tends to command the highest price in Boulder Opal world and can rival prices of the finest Black or Light Opal.

It’s really hard for me to pick a favorite type of opal, but when forced I always say Boulder Opal. Maybe because it’s a treasure I never knew existed or because it’s just freaking awesome!

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