Jewel Citizen looks at rare colour-change sapphires
Here’s a little ‘corundum conundrum’ for you – can a gemstone change from one colour to another? Well, yes and no.
Some gemstones, particularly the sapphire variety of the mineral corundum, sometimes show a remarkable shift in colour. Rare and exceptional specimens display a full change of colour. There’s no alchemy in this process, it’s just the presence of trace element impurities such as vanadium or chromium, in combination with a change in lighting conditions that causes this illusion. Nature’s conjuring trick can visually transform a blue sapphire to a purple or pinkish-purple one, or a purple example to pinkish-red. Who wouldn’t be captivated when their classic blue Princess Diana style sapphire ring scintillates a rich shade of purple by candlelight? Such sapphires are however the exception rather than the norm, and something very special for the enlightened few.
This Ceylonese sapphire changes from blue to violet…
and then to pinkish-purple
Those lucky enough to own one of these chameleon gems remark that it’s like owning two different jewels at the same time. Each stone is unique and possesses its own character. Personally I adore them and keep a weather eye out for new listings at auctions and for designers brave enough to use them in their collections. I covet them as unashamedly as a fashionista who longs for an Hermes Birkin bag.
Paradoxically a gem’s rarity can keep it relatively unknown, an example of this illustrated by the response from some jewellers I’ve spoken to who’ve never seen a colour-change sapphire. “Do you mean Alexandrite?” one once replied, citing the better-known green to red colour-changing stone first discovered in Russia in the early 19th century and popularised by leading jewellers including Tiffany. No actually I didn’t, but while on the subject of Alexandrite I’ll be posting soon about this amazing stone.
But let’s turn back to sapphires. Rarity and a lack of knowledge play a part in this more cautionary tale: I remember a few years ago being told by a friend about how a provincial auction house once listed a Belle Epoque ring with a bluish-purple stone as ‘an early twentieth century ring with large amethyst-type stone’. The guide price was in the low hundreds. My friend had seen the ring and said that the colour seemed different depending on the lighting. He thought little of it at the time. The ring ended up selling for a good few thousand pounds, and in my mind there’s no doubt that someone thought it actually contained a rare colour-change sapphire. It caused a stir for five minutes or so – antique dealers seem love it when an auction house ‘misses’ something and apparently the rumours were flying around the sale-room after the gavel fell. So assuming a large rare sapphire was mis-sold as an ‘amethyst-type stone’ the sale price was probably a fraction of its true value. Sadly without a full gemological report to confirm variety, origin, and any treatment to the stone it was never destined to realise its true value.
In the photos at the top of the article you can see a 15ct Art Deco sapphire ring under different lighting conditions: it appears blue or violet in daylight (candescent light), yet the same stone exhibits a remarkable change of colour to pinkish-purple in incandescent (in this case lamp) light. This is a colour-change sapphire in the true sense of the word.
A shift in colour, such as a subtle change from one shade of blue to another, is seen much more often than the rare and sought-after phenomenon of full colour change. When you’ve worn a colour-change stone it’s really hard to get excited about something that merely shifts colour to a slight degree.
Connoisseurs and collectors of these stones value them according to the degree of colour change above all other criteria, rating the change as weak, moderate or strong.
Many excellent examples of colour-change sapphires on the market come from mines in Sri Lanka (Ceylon) where they are still found to this day, although stones are also mined in Thailand and in parts of Africa. It is rare to find examples weighing in excess of 5 carats, and even more difficult to find larger examples that haven’t been heated to improve their colour.
A 1930s colour-change sapphire sautoir with an exceptionally large and impressive 76.11 carat stone was sold by Sotheby’s in Geneva in their Magnificent Jewels Sale in November 2011.
Something once considered a rarity reserved for gemstone collectors, these gems are now regularly achieving astounding sums at auction. In the November 2015 Magnificent Jewels Sale at Christie’s in Geneva, a 16.81 carat unheated colour-change Ceylon (Sri Lanka) sapphire ring realised CHF 389,000 ($388,485).
The Natural Sapphire Company has a great selection of sapphires in a variety of colours including some spectacular colour-change examples ranging from under a carat up to a little over 16 carats (as of June 2017). The great thing is that many of the sapphires come with full gemological reports from laboratories such as the GIA.
The photos above show a 5.08 carat violet to purple colour-change cushion-cut sapphire from The Natural Sapphire Company. The stone is unheated and untreated. It comes with a GIA certificate. This stone and a full inventory of sapphires, rubies, and jewellery can be viewed on the website www.thenaturalsapphirecompany.com (photo courtesy of The Natural Sapphire Company)
It seems like the secret of these amazing stones might finally be coming out. Jewel Citizen will be closely monitoring top jewellery auctions and designer trends for further developments.