A ruby is a variety of corundum, a very allochromatic mineral. It is the only substance which has a hardness of 9 on the Mohs scale of mineral hardness.Corundum is called ruby when it has inclusions of chromium. In fact, the presence of this element makes the allochromatic corundum red. A ruby can have different shades of red from a very vivid one (this is the typical colour of the famous variety of ruby called “blood red” or “pigeon blood”) to a pinkish red.Rubies are naturally found by searching through metamorphic rocks. The most important deposits in the world are the ones in Burma, however there are rubies mines also in Sri Lanka, Siam, Vietnam, China, Tanzania and Madagascar. It is possible to find deposits of rubies in Italy too, on mount Terminillo, though they are very small (1mm or 2mm).
Usually rubies are not very big, especially those
with a strong transparency. For this reason, rubies are considered exceptional when they are very clear and weight more than 10 carats.
A fundamental element in the cut choice is the quality of the raw stone. For the best gems it is used a faceting cut, while a cabochon cut is preferred when the stone is less transparent and when it shows the phenomenon of asterism. In fact, this last cut is the only one that displays the effect properly.
The name ruby comes from the Latin word rubeus (red). It is a very rare gemstone that has been used for centuries. It is possible to find very fine antique and vintage jewels. However, there are stones that for centuries were considered rubies to be recently discovered as something else. As a matter of fact, rubies, especially after the cut, could be confused with garnet or spinel. Luckily, the modern gemological techniques allow to analyse a stone and to discover its exact composition and nature.A resounding case of “faux rubies” regards the British Crown Jewels: The famous “Black Prince’s Ruby” and the “Timur Ruby” are not rubies but high quality spinels!
A natural ruby can be heat-treated but it is also possible to create a completely synthetic stone. It was Auguste Verneuil in 1902 who invented the first synthesis process, making ruby the first gemstone artificially reproduced in the history of gemology. His method (Verneuil Process or Flame Fusion) consists in melting a finely powdered substance, made by the same elements that compose a ruby, using an oxyhydrogen flame, and crystallising the melted droplets into a boule. However it is easy to identify these types of stones as synthetic because they have clear growth curves.
Ruby is most commonly used in the gemological field where it is set in unique jewels to exalt its beauty and rarity. Nevertheless, its market is wider than that. In fact, it is also bought by collectors and people who practice crystal healing. In this last case, it is preferred the ruby root.Ruby is the birthstone of July and the stone used to celebrate the fortieth wedding anniversary.