Watermelon Tourmaline Buying Guide


Summary
A perfect gem for a barbecue, watermelon tourmaline adds a fun and playful feel to jewelry. With summer in full swing, check out our watermelon tourmaline buying guide and learn the quality criteria for this colorful gem.
Reading time: 3 min 38 sec
Watermelon tourmaline slices dangle below brilliant green sapphires in these versatile dress up/dress down earrings. Design by Michael Endlich. Photo by Sarah Francis. © Pavé Fine Jewelry. Used with permission.

How Does Watermelon Tourmaline Form?

Rough tourmaline crystals form in elongated shapes underground. To be a true “watermelon,” this crystal should have a pink or red core with a green rind. The pink or red center of these crystals forms first. Then, a shift in chemistry in the geothermal fluid that creates the crystal occurs. Instead of manganese, which causes the pink color, iron enters the solution, which imparts a green hue to the crystal.

Watermelon tourmaline buying guide - rough
This large, gemmy crystal has a deep pink interior and a thin green rind. Slices of this crystal would look like a cross-section of watermelon. © Rob Lavinsky, www.iRocks.com. Used with permission.

While bi-color and parti-color tourmalines with color transitions along the longer axis of the crystal also form, these aren’t considered watermelon tourmaline. Nonetheless, some dealers refer to any bi-color pink and green tourmalines as watermelon tourmaline.

Watermelon Tourmaline Buying and the Four Cs

The IGS tourmaline value listing has price guidelines for tourmalines.

Color

By far, the most important criterion for assessing the value of watermelon tourmaline is color. Traditionally, this gem has a pink center with a ring of green around the edge. Sometimes, a colorless ring separates these colors. “Reverse” watermelon tourmalines, with a green core and pink edge, also occur. In addition, because tourmalines can form in any color of the rainbow, other color combinations may occur. While these aren’t traditional “watermelons,” a specimen with these rarer colors may fetch a good price.

watermelon tourmaline buying guide - rare colors
These tourmaline slices reveal some rare color combinations, with tri-color stones including rare blue hues. The rightmost slice is a typical watermelon tourmaline. © Rob Lavinsky, www.iRocks.com. Used with permission.

To grade color in watermelon tourmalines, consider each color separately. A saturated, deep red or pink is more valuable than a lighter tone. The green-hued area should also be saturated and may even reach darker tones than the pink or red. Each hue should be distinct, with no zoning in tone. Ideally, the transition between hues is abrupt, with no fading or brown zone between colors (though a colorless zone between green and pink is common). The proportion of pink area to green rind also affects value. A more watermelon-like proportion is desired, with a relatively thin green area around the pink core.

watermelon tourmaline buying guide - necklace
Watermelon tourmaline slices are an excellent way to create matching gems. In this necklace, 11 faceted pink and green tourmalines accompany 17 watermelon tourmaline slices. This design by Jason Baskin and Carol Demarco took an honorable mention from the Jewelers of America’s CASE Awards 2017. © The Gem Vault. Used with permission.

Clarity

Because watermelon tourmalines grow in an area of changing water chemistry, a specimen with good clarity is rare. Imperfections are tolerated, especially in the color transition zone. In addition, black inclusions on the pink area of the stone are highly salable for their resemblance to watermelon seeds.

Cut

While watermelon tourmalines are commonly sold as slices, some lapidaries create cabochons. Cabochons may be especially attractive options for specimens with a lighter center color and darker rim, as the shape can deepen the core and lighten the edges somewhat. Faceted rose cuts are also available.

watermelon tourmaline buying guide - sugarloaf cabochon pendant
Cut in a sugarloaf cabochon, this 8.51-ct watermelon tourmaline has a thin green rind. Design by Michael Endlich. Photo by Sarah Francis. © Pavé Fine Jewelry. Used with permission.

Carat

Price per carat doesn’t vary much for this gem, making it an affordable choice even in larger sizes.

Jewelry Considerations

While tourmaline is a tough gem that resists scratching, watermelon tourmalines may be susceptible to breaking. Surface-reaching inclusions or fractures can weaken the gem, making it more likely to break. Gems set in rings and bracelets are likely to experience accidental knocks, so this gem may be best in a pendant or earrings.

About the author
Addison Rice
A geologist, environmental engineer and Caltech graduate, Addison's interest in the mesmerizing and beautiful results of earth's geological processes began in her elementary school's environmental club. When she isn't writing about gems and minerals, Addison spends winters studying ancient climates in Iceland and summers hiking the Colorado Rockies.
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