As the market for coloured gemstones continues to grow stronger, consumers are starting to seek out gems with a difference, and stones that can offer two colours in one are certainly an eye-catching proposition.

There are a number of gemstones that split into two colours, and it is a naturally occurring process. Ametrine, for example, is a combination of amethyst and citrine fused together, created by the two quartz stones developing side by side but at different temperatures underground. The resulting gem is a clash of orange and purple.

Sheldon Bloomfield works with exceptional two-tone gems including the ametrine set in this ring. 

Margery Hirschey brings an artistic flair to her collections with mismatched and two-tone gemstones. 

Other gems that display two colours include watermelon tourmaline that splits between pinkish-red and green, two-tone citrines that flow from orange into black, colour-changing sapphires that can morph between colours such as blue and yellow, and two-tone quartz.

These earrings from Holts London star a pair of watermelon tourmalines. 

Marco Bicego has juxtaposed slices watermelon tourmaline with blue sapphires. 

There are two very different methods of designing around these gems. Some jewellers will look for stones with a perfect 50-50 split meeting in the centre that offers balance and symmetry, and historically these gems have commanded the highest prices.

Alternatively, designers will embrace the chaos of a stone that may offer a swirl of colours with no clear boundaries, blurred lines or a target effect with concentric circles of colour. These non-conformist stones work well in more organic, relaxed designs.

 A newer lapidary technique used to cut two-tone stones sits somewhere in the middle of these two distinct styles. It has been dubbed the sunburst style and rather than cutting the stone with equal parts of colour, it creates a gem with a swathe of one colour in the centre, surrounded by the other.

Online retailer Gemporia has a wide selection of jewellery set with sunburst ametrine. 

Whether used to bring perfect symmetry or some wild artistic expression, two-tone gemstones offer a peek into the mastery of geology for jewellery buyers seeking something a little off the beaten track.  

Beth Gilmour, part of London Fashion Week’s Rock Vault initiative, worked with two-tone citrine for her Dichroma collection.

Article from www.jewellerynetasia.com