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Royal Green
Royal Green As garnets go, demantoid is far and away the most famous and revered within the jewelry industry. It was the garnet of royalty, beloved by the Russian Imperial Family. It was a favorite decoration of Peter Carl Fabergé to use on his famous eggs, and it crossed into prominence in the Western Hemisphere thanks to the work of George Kunz and his buying power for Tiffany & Co.

Nowadays, few people outside of the jewelry industry even know about demantoid, and that’s a real trag-edy. If a jeweler is lucky enough to carry a few fine stones, many customers may be offset by the price, compared to the pyropes and almandines most people associate with the word “garnet.”

So what’s the big deal about demantoid? Why was it so popular back in the day? Why is it so expensive now? And what’s all this business about horsetails people rave about whenever demantoid is mentioned?

Well, here’s the scoop…
The best demantoids are colored by traces of chromium, the same element that gives the best emeralds their unrivaled green. Rich green doesn’t describe it properly. Given its favored status of the Romanov Family, royal green might be a more suitable appellation.

Andradite garnets, of which demantoid is a member, are known for dispersion or “fire:” the breaking up of white light into its spectral colors. It is this property for which diamonds are so appreciated. In fact, andradite has a numerically higher dispersion value than diamond.

What does that mean to the eye?
Just like in a diamond, you’ll see lots of flashes of red, orange, yellow, green, blue, indigo, and violet coming from inside a well-cut gem. It’s really amazing to see in person.

Demantoid’s dispersive display can be subdued by dark body colors, lots of inclusions, and poor cutting. Gems with deep body color mask the higher wavelength colors in a dispersive display, but you’ll still see lots of red and orange flashes.

What to look for:
As with all gemstones, there are varying levels of quality with demantoid garnet. Demantoid, however, is an odd duck in the world of colored stones.

Above all, color and size are the coin of the realm. The green shouldn’t be so dark as to affect the trans-parency of the stone, and it should be pure and vivid with as little brown or yellow undertones as possible. Demantoids over a carat are pretty rare, and fine Russian gems over two carats are exceptionally rare; like, most people in the jewelry industry may go their entire careers without seeing a fine Russian deman-toid over two carats. The Smithsonian Institute has an 11.52ct Russian demantoid on display.

Finish gems above five carats are not uncommon from Namibia and other sources, but again, the green body color usually has very strong yellow or brown undertones. Naturally, price goes up quickly with gems heavier than a carat, and the richer the green, the richer the price tag.

But…

Due to demantoid’s high dispersion, there is a trade-off between depth of color and dispersive display. As discussed earlier, the richer the color, the lower the dispersive display; the paler the stone, the greater the dispersive display. Many consumers favor one or the other: rich green or high dispersion. So color is a relative term when discussing demantoid garnet. Get what appeals to you. Still, the best greens always command the most in the market.

Clarity is another relative term regarding demantoid garnet. In just about every other gemstone in the world, a lack of inclusions is considered better than having inclusions.

Again, but…

Demantoid garnet is known for inclusions that are affectionately called “horsetails.” In layman’s terms, they’re yellowish needle-like streaks that look like horsetails. They are often eye-visible, too, which is even more unusual for them to be considered an aesthetic plus, and if they’re well-formed in a stone, you might actually have to pay a premium.

Wait. What?

Why are eye-visible inclusions a positive thing for demantoid garnet? First, horsetails are absolutely con-clusive of the species as far as identification goes. Second, horsetails are highly, highly indicative (alt-hough not definitive) of Russian origin (translated “collector’s value”).


By Smallru (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons
Provenance is something else to be considered, although not dogmatized. Ask any industry expert, and they’ll tell you the finest demantoids ever brought to the surface are unarguably from the Ural Mountains. The chromium deposits in the Urals are responsible for the famous green of Russian demantoid, and few stones from other locales ever come close to that luxurious green. Some extraordinary stones have been mined in Italy, Iran, more recently in Namibia, Madagascar, and a few other locations, but most of the tippity-top stones in the world probably came from Russia. But always let a stone do its own talking.

Care and Cleaning
Demantoid garnets set in jewelry are a rare and special treat, and they should certainly be treated as such. Jewelry is meant to be worn and enjoyed because, let’s be honest: what good is a beautiful gemstone if it isn’t suitable to be worn and shown off? But this is a blog from a jewelry store, so we’re biased.

But here are a few suggestions when it comes to demantoid.

Garnets are wonderful jewelry gems with great wearability, but there is some variance in hardness and toughness among the six different species. Andradite, the family of demantoid, is the softest of the bunch; next to uvarovite, it’s prone to chipping and scratching more than the other gem garnets.

Pendants, earrings, and brooches are excellent choices for demantoid. It’s certainly hard enough to be worn in rings and bracelets, but it would be advisable to reserve those pieces for special occasions, other-wise you’ll start to see nicks and chips on the stones.

Like all garnets, demantoid is attacked by hydrofluoric acid, so keep it away from cleaners made for re-moving rust and hard-water stains. Ultrasonic machines are safe, but steam cleaning is risky; it’s best to avoid it with a rare stone like demantoid.