Distinguishing Features
Ruby command the highest per-carat price of all coloured stones. The record is $1,266,901 per carat, when a 25.59-carat ruby ring was sold in an auction held by Sotheby's Geneva on May 12, 2015.
Rating 9 on the Mohs hardness scale, ruby is ideal for frequently worn jewellery.
The Most Desirable Picks
Colour: The most valuable ruby colours are red to slightly purplish red with medium to medium-dark tone and vivid saturation.
Clarity: Depending on how visible the inclusions are, rubies with lower transparency or brightness due to inclusions are less valuable. However, inclusion free rubies are scarce; people in the trade expect rubies to have at least some inclusions.
Cut: A skilled cutter would decide the cut for rubies according to their rough crystals. Factors such as pleochroism directions, crystal shapes would suggest the best cut for a specific gemstone.
Carat Weight: Commercial quality rubies are commonly available in all sizes, while fine quality rubies over one carat are very rare. The price per carat increases significantly with its size, especially for fine quality rubies.
Most renowned origins: The most renowned rubies are from Myanmar, Afghanistan, and northern Vietnam.
Origins
Many rubies in the market are associated with source names. It does not guarantee the stone is from a specific source. Usually, the quality of the stones under description might be typical of that source or represent the finest stones from that source. But a single source does not yield gems of all the same colour and quality. Reputable labs can provide country-of-origin reports with more accurate information.
The source name used in the trade may indicate the following qualities:
The finest “Burmese” rubies, often described as “pigeon’s blood” rubies:
· red to slightly purplish red hue,
· vivid saturation and medium-dark tone,
· Minute inclusions
· a glowing red fluorescence under ultraviolet light.
“Thai” and “Pailin” describe rubies:
· can be pure red, brownish red to purplish-red hue,
· medium dark to very dark tone;
· lack red fluorescence
· have black extinction areas
“Mozambique” describes fine quality rubies with different characteristics, such as less fluorescence.
In GIA’s description, “crimson” rubies are rich, slightly purplish red, and “scarlet” rubies are red with a slight hind of orange.
The map shows the major sources of ruby mines worldwide. Myanmar, Mozambique, Tanzania, Madagascar, Malawi, and Kenya in Africa have some commercially mining resources.
Significant Pieces
The Queen’s Burmese Ruby Tiara is one of the most symbolic and personal pieces created for Her Royal Highness by the House of Garrard. The 96 rubies mounted in the tiara were originally given to the queen as a wedding gift from the people of Burma, intended as a symbol of protection against illness and evil.
Formation
Ruby is a variety of corundum, which is made of aluminium oxide. Corundum can form only in an environment with low silicon content and under the right temperature and pressure. Corundum is colourless in its purest form. The colour of ruby is caused by the trace element of chromium in corundum. These specific requirements make ruby rare.