Meet the Gemstones: Pink Zircon
The month of October is the month of opals. Though less well known, it is also the month of rose or pink zircon. In inexpensive birthstone jewelry, rose zircon has often been represented by a pink synthetic spinel or synthetic sapphire. Today it is more likely to be represented by a pink cubic zirconia.
ABOVE: This lovely 7.20 carat salmon-pink colored, Super Trillion-cut zircon, was cut by John Dyer. Note the visible doubling of facets as you look through the stone. Photo by David Dyer, courtesy of John Dyer Gems.
Despite the similarity in names, zircons are not related to cubic zirconia, an entirely different animal—or rather, man-made mineral. Zircons are natural gemstones commonly found in the gem gravels of Southeast Asia: Myanmar, Thailand, and Sri Lanka.
Zircon Gemstone Attributes
Zircons are interesting stones, gemologically speaking, as they may contain radioactive elements as impurities. Over time—geologic time—the radioactivity can break down the gemstone’s structure and alter its optical and physical properties. For this reason, zircons are often classified as “low” (having the most radioactively induced damage to their structure—these are mostly greenish), “medium,” and “high,” this last being the type most commonly seen in the jewelry industry. At the low end, the stones have lower RIs and lower hardness (about 6 on the Mohs hardness scale). They may also be less doubly refractive. “High” zircons have higher RIs, more doubling, and their hardness is 7 to 7.5.
Zircons are commonly heat treated to colors ranging from colorless, to cinnamon, sherry, yellow, orange, pink, and red. The most commonly sought color is blue. The colorless variety has been used as a diamond imitation because of zircon’s diamond-like luster and high dispersion. Fascinatingly, heat treatment can actually repair some of the damage done to the crystal structure as well as change the stones’ colors, according to GIA’s Gem Encyclopedia.
Heat treatment, however, can cause brittleness in zircons. It’s not uncommon to see blue zircons that have been worn in a ring or carried in a paper with other zircons that show abraded facet junctions.
Zircons are strongly doubly refractive, which makes them pretty easy to separate from other gemstones that come from the same regions. Look through a zircon with a loupe and you’ll quickly see doubling sets of facet junctions. Though you can see this under magnification in other doubly refractive stones, if you look for it, in zircons the doubling is so strong, it’s impossible to miss. (You can see it in the images we have here.)
Natural Brownish Zircon
Untreated, zircons are often greenish or brownish. A large brownish zircon saved my bacon when I took my 20-stone gem exam for my GG. It was the first stone in my set. It was as large as a thumbnail, well cut, and beautiful. I was going to identify it as a smoky quartz—strictly by appearance. I quickly learned that “sight IDs” can be very dangerous.
When I looked inside just to see what inclusions might be there, I was shocked by the strength of the doubling—something no self-respecting quartz would show. I immediately took an RI, saw the characteristic rainbow flash telling me that the RI was over the limits of the refractometer, and began to suspect what I was really looking at. Having that stone first in my test made me slow down and be suspicious of every stone that came after it, allowing me to pass the test the first time. I’ve had a fondness for brown zircons ever since.
Circling back to pink zircons . . . Though rose “zircon” birthstone jewelry is very common, the real thing is very rare. Rather than a true pink, the color is often more salmon or orangish pink, as you can see in these images of stones cut by John Dyer, and the brownish-red pink zircon from Josh Saltzman at Gems by Nomads. But they are undeniably beautiful.
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Sharon Elaine Thompson is a GG and FGA who has been writing about gemstones and jewelry for Lapidary Journal Jewelry Artist since 1987. She also writes a line of birthstone romance novels under the name Liz Hartley.