Today, jewellers use many varieties of blue stones: sapphire, tanzanite, aquamarine, topaz, tourmaline, spinel, kunzite, azurite, agate, and more. Out of those, we believe, sapphire and tanzanite are the most precious ones.
Sapphire
Sapphire means 'blue stone' in Ancient Greek. It is a variety of corundum, a very hard mineral rated at 9 on the Mohs scale. Other corundum varieties, e.g. yellow, orange, pink, green, and others, are also called sapphires, with the exception of the red variety. Some sapphire feature the alexandrite effect of changing colour depending on the lighting type. Star sapphires’ special structure forms an optical asterism inside, usually with six rays. A single-ray effect is called a cat’s eye.
In Russia, blue sapphire circulation throughout the country is regulated by the Federal Law 41-FZ “On precious metals and gemstones”.
Deposits
There are plenty of sapphire deposits around the world, i.e. in Russia (South Urals, Far East), yet few of them produce truly precious stones. The most valued, cornflower-blue Cashmere sapphires were once mined for at the border of India and Pakistan, in Cashmere province. Bright purple gems were found in Sri Lanka, and large plum-coloured stones used to be brought from Myanmar. Relatively clear sapphires of beautifully intense colours are currently brought from Tanzania, Australia, Nigeria, South-Eastern Asia, USA and Madagascar.
Unique qualities
Back in ancient times, sapphires were often used as mascots and decorations. Attention-seeking women offered men drinks in sapphire bowls and wore sapphire earrings hoping for a happy marriage. The gems were believed to bring loyalty and humbleness while keeping treachery and envy away, to establish peace and to keep travellers safe.
Sapphires have always been seen as a symbol of royal power and thus adorned dynasty regalia like crowns and scepters. Some of the larger faceted sapphires are kept in state and national collections. For example, Russia’s Diamond Fund exhibits the Imperial Globe with a 200 carat Ceylon sapphire on its top. It also owns a brooch featuring a cornflower-toned sapphire of 258 carat. The British monarchs own the Stewart Sapphire and the St. Edward’s Sapphire; the Star of India eastern star sapphire is also very famous.
Cutting
When processing a sapphire, good cutting is essential to emphasize the natural beauty of the gem. For clear sapphires, brilliant, step or mixed (brilliant on top and step below) cuts are used on shapes varying from Round and Oval to Baguettes and Octagons. Star sapphires and cat’s eye sapphires are traditionally cut en cabochon.
Tanzanite
Tanzanite is a type of zoisite, the blue-coloured mineral that is pretty soft at 6.5 to 7 on the Mohs scale. Tanzanites are promising investment gems, specifically larger (10+ carat) highest clarity stones or rare collection pieces. Large (2+ carat) tanzanites can be priced at over USD3,500 per carat.
Deposits
The only deposit is located on the north of Tanzania, at the foot of Kilimanjaro. The gemstone was first discovered in 1967, with Tiffany & Co. inventing the name for it that was accepted by the mineralogists.
The world’s largest, indigo tanzanite is named Mawenzy after Kilimanjaro’s second highest peak and weighs 16,839 carat, that’s over 3 kilos. Tanzanite is already scarce, thus collectors and connoisseurs are quick at purchasing the gem that will soon become a rarity.
Unique qualities
Tanzanite is the embodiment of the mysterious African continent, a gem that enchants with its one-of-a-kind beauty and the extraordinary depth of colour. It features the alexandrite effect of changing colour depending on the lighting type. Under artificial light, tanzanite turns to purple, and under luminescent light, to royal blue with a hint of fuchsia.
For ages, it has been a symbol of love and luxury, career success and family peace and serenity. Tanzanite-holding pieces make women more attractive and confident as well as sensual and appealing. Today, tanzanite is the choice of the most sophisticated ladies with impeccable style and strong personality.
The stone needs care. It can only be soap-washed as it does not stand acids or even UV baths. It can also be hurt by sharp temperature changes. For those reasons, tanzanite is rarely worn casually but rather kept for special occasions only.
Cutting
Tanzanite requires most careful cutting and setting. Brilliant, step or mixed cuts are used for various shapes, Round and Oval to fantasy ones.