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July Birthstone: Ruby
Rubies are one of the most sought after gemstones in the world. Belonging to the family Corundum, chemical formula Al2O3, rubies have two parts aluminum and three part oxygen. Sharing the same chemical composition as sapphires, rubies are coloured by traces of chromium and titanium to achieve its magnificent red colour. Rubies have a hardness of 9 on the Moh’s Scale of Hardness behind Diamond, the hardest natural material in the world. Rubies are essentially red corundum/sapphires. Determination of a gemstone as ruby requires the right amounts of titanium and chromium. Lack of which will classify a light red or pink corundum, a pink sapphire, rendering the gemstone less valuable. Rubies have been worn by aristocrats and royalty since the dawn of time. Ruby is derived from the Latin word rubber which means red. Folklore states that rubies are known to ward off sickness and to make one invulnerable to defeat. During ancient times it was said that those that possess Rubies will never have their wealth or belongings taken from them. Today, Rubies are used for the highest quality jewelry pieces and can be extremely beautiful in rings, charms, earrings and bracelets. Gem quality rubies over five carats are rare. Rubies of over five carats in fine gem quality have always been hardly seen. In the 17th Century the great gem dealer Tavernier wrote: “when a ruby is of over five carats and of fine quality, it is paid whatever is asked of it”. Fine quality rubies typically originate from Burma(Myanmar), Sri Lanka, India, Thailand, East Africa andSouth America.
Treatments on Ruby Treatments on gemstones have been common throughout the ages. Treatments which enhance the appearance of the gemstone will yield higher prices. Treatments such as heat treatments, lead glass filling and heat diffusion treatment. The most common treatment is the application of heat. Most if not all rubies at the lower end of the market are heat treated on the pre cut/rough. This process is done to improve color, remove purple tinge, blue patches and silk inclusions. These treatments usually occur around 1800°C (3300°F). Low tube heat, another process to enhance rubies is when the stone is heated over charcoal of a temperature of about 1300°C (2400°F) for 20 to 30 minutes. The silk is only partially broken as the color is improved.A less acceptable treatment, which has gained notoriety in recent years, is lead glass filling. Filling the fractures inside the ruby with lead glass dramatically improves the transparency of the stone, making previously unsuitable rubies fit for applications in jewelry. The process is done in four steps:The rough stones are pre-polished to eradicate all surface impurities that may affect the process The first heating process is done after being cleanse with hydrogen fluoride, to remove all impurities within the cavities and openings. Temperatures can go as high as 1400°C (2500°F) but the process most likely occurs at a temperature of around 900°C (1600°F) to keep the rutile silk is still intact. The second heating process in an electrical oven with different chemical additives. Although alternate solutions and concoctions been successful, lead-containing glass-powder is the primary agent used. The ruby is oiled, then covered with powder, embedded on a tile and placed in the oven where it is heated at around 900°C (1600°F) for one hour in an oxidizing atmosphere. The orange colored powder transforms upon heating into a transparent to yellow-colored paste, which fills all fractures. Upon cooling, the color of the paste is fully transparent, which improves the overall transparency of the ruby. If a colour or hue needs to be achieved, copper or metal oxides such assodium, calcium and potassium are added to the mixture.
The following are the optical and physical properties of Ruby which is consistent to the corundum family.
Composition: Al2O3 Specific Gravity: 4.00 Colour: Red Colour: Violet, pale reddish violet Transparency: Transparent Moh’s hardness: 9 Crystal System: Hexagonal (trigonal) Refractive index: 1.762-1.77 Birefringence: Doubly Refractive +0.008 Pleochroism: orangey red-purplish red Fracture: uneven or Conchoidal Cleavage: None
For more information on ruby and any gemstone please contact us by email or by phone at 416 360 1381.