From rare pink star diamond to black opal, we’ve all seen our fair share of exceptional gemstones. Yet one particular kind never fails to amaze — bi-coloured gemstone.
“A bi-coloured stone is like a paintbrush loaded with more than one colour,” says US-based jewellery designer Margery Hirschey, who likes to take a painterly approach to her designs. “It’s just so much more interesting to have slight or bold colour variations within one stone than a solid colour stone without any subtle variations.” Aside from looking more natural, Hirschey says bi-coloured gemstones work pretty much on any design where colour dominates.
DICHROMA QUARTZ PENDANT IN BLACK RHODIUM AND YELLOW GOLD, by BETH GILMORE DICHROMA BI-COLOURED RINGS, by BETH GILMORE
Watermelon tourmaline, ametrine, and topaz are the most common of these unusual stones. Other gemstones like tanzanites and sapphires also show such effect, but on very rare occasions. “Bi-coloured gemstones are the amazing works of nature,” shares artisan jeweller Wallace Chan. “The dual colours are like inseparable twins or lovers meant to be together.”
What’s behind this rare occurrence is the presence of more than one impurity or pressure condition during the formation, which causes the stone to have multiple colour effects. With the uncertainties that surround their creation, no two bi-coloured stones are the same or have the same colour ratio. Finding these unique miracles of nature is very rare and could take years. And this erratic supply significantly adds on to their market value.
TSAR RING IN 18K YELLOW GOLD, AMETHYST, CITRINE AND AMETRINE, by ANNOUSHKA
TSAR FEATHER EARRINGS IN 18K YELLOW GOLD, AMETHYST, CITRINE AND AMETRINE, by ANNOUSHKA
Although some gemstones are available in a rainbow-like array of colours, there are times when unseen colour combinations are also found. But these are usually sold off within hours, picked up by jewellers or collectors even before they are presented in the market.
Watermelon tourmaline got its name from the watermelon, and its colours can range from deep, rich green to a clear pale green, and from fuchsia pink to a translucent baby pink. There are also other bi-coloured tourmalines where the hues can range from blue to green to teal to greenish-yellow.
UNICO EARRINGS, by MARCO BICEGO
Almost too strange to be real, ametrine, as the name implies, is a combination of two members of the quartz family — amethyst and citrine. For this type, the colour zoning ranges from a vivid violet-purple to bright golden-yellow. Apart from two different ways of oxidation of iron impurities, ametrine also needs two different temperature conditions to bring out such lovely colours. Topaz is another gemstone family that is found in a wide range of colours, and bi-coloured topazes make for stunning centre stones. The most beautiful of bi-colour topazes range from orange to red, golden to blue, and at times with shades of green and yellow.
EARRINGS IN 22K GOLD AND 14.57CT WATERMELON TOURMALINES, by MARGERY HIRSCHEY
BROOCH WITH CARVED WATERMELON TOURMALINE, by LYDIA COURTEILLE
Jewellery designers love these quirky colourful gemstones and use them prominently to add drama to their jewellery. “I love bi-coloured gemstones,” shares Parisian jewellery designer Lydia Courteille. “Our goal as designers is to wake up the colours that are sleeping. I love working with some matte materials with bi-coloured gemstones to create a contrast.”
The stones’ organic nature lends a natural element to the designs, and these imperfect characteristics make each jewellery piece one of a kind. Mostly found in linear forms, the stones are generally shaped in baguettes or step cuts, except for watermelon tourmalines that are round by nature and are thus faceted in discs imitating the real watermelon fruit.
This article was originally published in Solitaire 90, The Colours Edition.