The word ruby comes from ruber, Latin for red. The color of a ruby is due to the element chromium
A Ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide).
The quality of a ruby is determined by its color, cut, and clarity, which, along with carat weight, affect its value. The brightest and most valuable shade of red called blood-red or pigeon blood, commands a large premium over other rubies of similar quality.
Mines of Ruby
The Mogok Valley in Upper Myanmar (Burma) was for centuries the world’s main source for rubies. That region has produced some exceptional rubies, however in recent years few good rubies have been found. In central Myanmar, the area of Mong Hsu began producing rubies during the 1990s and rapidly became the world’s main ruby mining area. The most recently found ruby deposit in Myanmar is in Namya (Namyazeik) located in the northern state of Kachin.
Rubies from Mozambique( Africa ) are very popular now a days. Rubies have also been mined in Thailand, in the Pailin and Samlout District of Cambodia, as well as in Afghanistan, Australia, Brazil, Colombia, India, Namibia, Japan, Scotland, Madagascar, Nepal, Pakistan, Tajikistan, Tanzania, Thailand (Siam) and Vietnam. In Sri Lanka, lighter shades of rubies (often “pink sapphires”) are more commonly found. The Republic of Macedonia is the only country in mainland Europe to have naturally occurring rubies. They can mainly be found around the city of Prilep. Macedonian rubies have a unique raspberry color. A few rubies have been found in the U.S. states of Montana, North Carolina, South Carolina and Wyoming.
All natural rubies have imperfections in them, including color impurities and inclusions of rutile needles known as “silk”. Gemologists use these needle inclusions found in natural rubies to distinguish them from synthetics, simulants, or substitutes. Usually, the rough stone is heated before cutting. These days, almost all rubies are heated in some form, with heat treatment being the most common practice.Unheated and untreated rubies of high quality command a large premium.
Some rubies show a three-point or six-point asterism or “star“. These rubies are cut into cabochons to display the effect properly.These are called as Star Ruby. Aster isms are best visible with a single-light source and move across the stone as the light moves or the stone is rotated. Such effects occur when light is reflected off the “silk” (the structurally oriented rutile needle inclusions) in a certain way. This is one example where inclusions increase the value of a gemstone.
The most common treatment is the application of heat. Most rubies at the lower end of the market are heat treated to improve color, remove purple tinge, blue patches, and silk. These heat treatments typically occur around temperatures of 1800 °C (3300 °F). Some rubies undergo a process of low tube heat, when the stone is heated over charcoal of a temperature of about 1300 °C (2400 °F) for 20 to 30 minutes. The silk is partially broken, and the color is improved.
Another treatment, which has become more frequent in recent years, is lead glass filling. Filling the fractures inside the ruby with lead glass (or a similar material) dramatically improves the transparency of the stone, making previously unsuitable rubies fit for applications in jewelry.some of the Gems lab write “Heated with foreign substance” for lead filled rubies.