Or parti-coloured tourmaline, to give it its correct title. Not, as my slightly po-faced GIA instructor said, as in, ‘let’s have a party.’ That may have been a joke. It was slightly hard to tell. New in stock, I have more pieces of this most beautiful and fascinating of stones in a breathtaking array of colours. I have new slices and some rose cut (polki) pieces, and each piece has been hand-selected by me for either its pattern – complex or simple, its colour – unusual or gorgeous, its unusual combinations of colours, or it’s saturation – saturated or subtle. The green and orange polki, top left, or the teal green surrounded by black slice towards the top right; the pale pink and blue polkis, of which I have several, and blue is always a popular colour that goes fast.

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Clarity of these stones can be rather mixed, but most of these are not bad and many have the kind of clarity characteristics that I think are rather beautiful; for instance you can see mirror-like inclusions on several of the stones, which sparkle as the light catches them with a spectral flash. Tourmaline crystals are very distinctive; broadly triangular in shape with striations down the sides and the colour zoning is due to a change in the concentration or composition of the trace elements that give the stone its colour during its growth. Iron, titanium and manganese induce different colours and yet others might be due to colour centres caused by radiation. To shop watermelon slices, click here;  to shop freeform rose cuts (polki), click here.

So many gorgeous examples of watermelon tourmaline jewellery around, but if I had to pick out one I have long coveted Barbara Heinrich Studio’s watermelon tourmaline slice necklace. This also has hand-fabricated 18k gold shell elements and gold tube spacers. Love those gold shells, echoing the shape of the tourmaline slices, and love the matched-but-not-matched slices.

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