Professional Jeweler Archive: Watermelon Garnets

April 2000

Gemstones & Pearls/Gemology

Watermelon Garnets

A rare mixed gem reappears on the market with a brand new name

After a half-century hiatus, an interesting variety of hydrogrossular garnet mixed with idocrase is on the market again. The best examples are translucent and exhibit variations of vivid pink, red and green.

The mixed gem was last found in the 1940s in South Africa’s Transvaal region. Because of its similarity to fine jade, it was called Transvaal jade.

A few textbooks – including Gems, Their Sources, Descriptions and Identification by Robert Webster (Butterworth & Co. Publishers Ltd., 1983) – describe this variety of garnet gemologically. But the gem was never widely available in good qualities, which kept it from becoming a mainstream product.

One gem cutter in Idar-Oberstein, Germany, saw the gem’s potential in the 1940s and managed to stash several tons of rough. The heap sat in his inventory – and later his son’s inventory – until now.

On a recent trip to Germany, U.S. gem dealer Bill Heher saw, fell in love with and bought the inventory – all four tons of it. “About 3.5 tons were junk, 500 kilos had better color but was highly fractured and about 50 kilos are superb,” he says. Heher’s company, Rare Earth Mining Co., Trumbull, CT, now sells the gems mostly as cabochons, though some faceted material is available. The reemergence of this hydrogrossular garnet suggests a review of its differences from jade may be helpful to you.

Gemological Aspects

Garnet-idocrase ranges from opaque to translucent, depending on quality and thickness when cut. Mostly cut cabochon-style, the gem could be confused with jade because of its mottled appearance and colors. The Gemological Institute of America studied several specimens and reported on them in the Spring 1999 issue of its quarterly journal Gems & Gemology. GIA identified the green portion of the gems as idocrase and the pink to red portions as hydrogrossular garnet. The gems contain areas where the two species are mixed to such an extent they’re almost impossible to separate gemologically. GIA attributes the red and pink to manganese and the green to iron, not chromium as was once theorized.

Marketing Aspects

Heher markets the gems as watermelon garnet. “We’ve all heard about watermelon tourmaline – the name is also a good fit for this kind of garnet because of the colors,” he says.
Heher says the fern-like and tree-like inclusions in hydrogrossular garnet make it easier to sell.

“Some gems take on the appearance of gorgeous landscape paintings,” he says. The color is another selling point. “There’s a lot of selling potential in the rosy red and kelly green. It’s a beautiful color palette for designers and jewelers.”

David Wright, a retail jeweler in Willington, CT, says the gem appeals to customers who like the unusual and who like handcrafted designs. “I also show them to people whose birthstone is garnet; they’re always amazed at the rich variety of garnets available.”

In the final analysis, rarity is probably watermelon garnet’s greatest selling asset – and liability. In the years ahead these gems will remain beautiful and coveted conversation pieces – until the day they finally run out.

  • Rare Earth Mining Co., Trumbull, CT; (203) 378-8672.

– by Robert Weldon, G.G.

Garnet-Idocrase vs. Jade

Below are some gemological differences between the garnet-idocrase blend and jade.
Jadeite Jade
Refractive Index
Specific Gravity
Line at 466nm
Line at 437nm*
Mohs Hardness
* Chromium containing jade shows absorption lines at 655, 690 nanometers. (Nanometer – which is 1 millionth of a millimeter – describes a specific area in the electromagnetic spectrum.)

This suite of watermelon garnets shows a range of color and fern-like inclusions. Gems are courtesy of Rare Earth Mining Co., Trumbull, CT

Copyright © 2001 by Bond Communications