ISSUE 16
quality, 1-3ct facetted translucent gems can range from US$75-100/ct.
a centrepiece in the Imperial State Crown of England, is not a ruby at all, but a natural rough crystal of red spinel.
Rhodocrosite has a distinct cleavage, is relatively soft (H = 3,4-4) and should not be used in rings. Do not use steam or ultrasonic cleaning methods.
Origin
RHODOLITE Rhodolite is a light to dark purplish red garnet. It is paler than either pyrope or almandite.
Value
ROCK CRYSTAL The transparent colourless variety of quartz.
ROYAL LAVULITE
Royal lavulite cabochon.
Also known as sugulite or Royal azel (from the town Hotazel in the northern Cape, which is the gem’s only source). It is an opaque material with a striking purple colour and often used as carvings, beads and cabochons. It was discovered in the 1980s, promoted extensively and fetched quite high prices in the USA due to its unique colour. It is a tough stone with average hardness (5,5-6,5).
RUBELLITE
Rubellite, 10ct, from Namibia.
Rubies from the Magok mine in Burma (now Myanmar) are considered the finest due to their intense saturated red colour. This colour is often described as pigeon’s blood. Other sources are from Thailand, Pakistan, East Africa, Madagascar and Vietnam.
Rubellite is a term loosely applied to tourmaline with a pinkish-red to red colour. It is normally quite included and is priced for its colour – the more pure and intense reds are the most expensive. Prices normally range between US$65-90/ct.
The more saturated (intense) the colour, the more expensive. However, a slight variation in colour can affect value dramatically. Secondary colours of purple and orange may detract from the price. Pinkish overtones may increase the value. Size is also important, as large fine gems are quite rare. Fine 1ct Burmese rubies can range from US$2 500-4 500/ct, while extra-fine can fetch up to US$8 000/ct. Extra-fine gems larger than 5ct can go as high as US$20 000-30 000/ct. Fine rubies from other localities range in price from US$1 000-3 000/ct. However, small good-quality rubies which are normally used in jewellery should not cost more than US$600/ct. Enhancements Nearly all rubies have been heat-treated to improve their colour and clarity. Recently, a high-temperature process (whereby the elements beryllium and chromium are infused into the crystal structure) has been developed which dramatically improves the colour of rubies. The red colour of such gems is located only in its outer layer and, when chipped or re-polished, the colourless interior may become visible. These enhancements can easily be detected by a gemmologist and should be disclosed to the client. Synthetic rubies
RUBY Ruby is the transparent red variety of the mineral corundum (Al2O3). Trace amounts of chromium cause the colour. It is the birthstone for July. Oval cut ruby, 3,2ct.
Lore Ruby has long been recognised as a valuable gem. In Sanskrit, it is described as ratnaraj, the “king of gems” and in the Bible, it is mentioned as one of the gems in the breastplate of the high priest.The famous 170ct Black Prince Ruby, mounted as
Synthetic rubies have been made since the beginning of the 1900s. Since then, various methods of ruby synthesis were developed and synthetic rubies were sold worldwide as a less expensive alternative. To the jeweller, it is quite a challenge to distinguish between a natural ruby and those made by man, especially if the gem is relatively inclusionfree. Trade names such as Ramaura and Chatham are used to indicate the laboratory from where the synthetic ruby originates.