If one gem makes you think of summer, it’s surely watermelon tourmaline. This juicy-looking gemstone is aptly named – its colourful stripes of green and pink resemble a slice of our favourite refreshing fruit.
The word ‘tourmaline’ comes from the phrase ‘tura mali’, which means ‘stone of many colours’ in Singhalese, the language of Sri Lanka. It’s an apt name considering that tourmaline comes in a plethora of pretty shades.
Gemstones in the tourmaline family are boron silicates that vary in colour according to the elements present in the crystal structure. It’s a large family – there are actually 11 different species of tourmaline, differentiated by their properties and chemical composition. Watermelon tourmaline belongs to the species called Elbaite – a group which includes most of the multi-coloured varieties of tourmaline.
Watermelon tourmaline is formed in the cracks in volcanic rocks. A solution of water and various minerals seeps into these cracks and, over time, form a lattice of crystals. The crystal uses the mineral that fits most easily into the lattice and when the element is gradually depleted from the water solution, other elements are used instead, causing different coloured layers. The inner pink of a watermelon tourmaline is caused by lithium, chromium or manganese and the green outer by lithium, iron, titanium or vanadium. Sometimes the stone will have a paler layer between the pink and green.
Watermelon tourmalines were first discovered in 1902 in Maine, USA, at a mine in Newry. These days, it is mined in many other countries, including Brazil, Madagascar, Sri Lanka, Australia and Nigeria.
At 7-7.5 on the Mohs scale, watermelon tourmaline is resistant to nicks and scratches. However it is a brittle stone, so should be used with caution in everyday jewellery. A good jeweller will be able to place your stone in a protective setting. Indeed, it takes an expert to cut it well, as its complex structure and areas of tension makes a watermelon tourmaline difficult to cut without cracking it.
Shopping for watermelon tourmaline will introduce you to many creative pieces of jewellery, designed to bring out the fun and unusual qualities of this cheerful gemstone. Go on, have a browse and bring a little of its summer sunshine into your life!
Kim Rix, GG GIA
Be sure. Be smart. Buy with confidence
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