Watermelon tourmaline

Watermelon tourmaline is the name for tourmaline crystals with a pink or red centre and a green outside; sometimes a colourless ring lies between the two colours. Most of these stones are elbaite, a lithium-bearing kind of tourmaline. Dealers gave it the name because its colours resemble the rind and flesh of a watermelon. The colours arise when the trace elements around the crystal change while it grows. Its main sources are the Brazilian state of Minas Gerais and the US states of Maine and California.

Jewellery: To show off the colour pattern, designers often set thin slices of the crystal in pendants and earrings instead of faceting it. Clean stones are also faceted. Collecting: Crystals with sound terminations and distinct colour zones, and well-polished slices, are sought by collectors. Science: The colour zones are like a record of how the fluid around the crystal changed as it grew, and they are studied in mineralogy.

It has a hardness of 7–7.5 on the Mohs scale. It scratches glass and steel; a steel knife cannot scratch it. Its specific gravity is 2.9–3.4 g/cm³.

Its best-known localities: Cruzeiro mine, São José da Safira, Minas Gerais, Brazil; Dunton Gem Quarry, Plumbago Mountain, Newry, Oxford County, Maine, USA; Mount Mica, Paris, Oxford County, Maine, USA; Coronel Murta (Barra do Salinas district), Minas Gerais, Brazil; Himalaya mine, Gem Hill, Mesa Grande, San Diego County, California, USA.

Seen in cross-section, the crystal shows a pink or red core surrounded by a green rim; there may be a colourless ring between them. Its hardness is 7–7.5; it has no cleavage and is brittle. Its refractive index is about 1.614–1.666 and its specific gravity 2.90–3.40. Under short-wave ultraviolet light the pink core may glow a chalky blue or creamy white. Acid cleaning: in some stones dark inclusions are bleached with acid; this should be disclosed.

On the “street to diamond” value ladder it sits on step 5 of nine: Ornamental stone. The value of watermelon tourmaline depends most on lively colours and a sharp contrast between them: stones in which a vivid pink core and a distinct green rim form balanced, even rings are the most sought after. Compared with single-coloured tourmalines it is relatively affordable, but clean, vividly coloured stones and large stones over 10 carats are worth markedly more. In slices the quality of the cut and the absence of cracks that spoil the pattern matter; in crystal specimens, size and undamaged terminations count.

Today crystal-therapy websites and stone sellers claim that watermelon tourmaline opens and balances the heart chakra, increases love, joy and emotional balance, and eases stress. There is no scientific evidence that watermelon tourmaline increases love, joy or emotional balance. The two colours carry no meaning; they are a physical trace left by the trace elements (manganese for pink, iron for green) that changed while the crystal grew. This section reports beliefs; it is not health information. There is no scientific evidence for these claims and no stone replaces medical treatment.