Ruby is distinguished for its bright red color, being the most famed and fabled red gemstone. Beside for its bright color, it is a most desirable gem due to its hardness, durability, luster, and rarity. Transparent rubies of large sizes are even rarer than diamonds. Ruby is the red variety of the mineral corundum. Sapphire, the other gem variety of corundum, encompasses all colors of corundum aside from red. In essence, ruby is a red sapphire, since ruby and sapphire are identical in all properties except for color. However, because of the special allure and historical significance, ruby has always been classified as an individual gemstone, and is never identified as a form of sapphire (though some purplish-red colors may straddle the line of being classified as either ruby or sapphire). In the United States, a minimum color saturation must be met to be called a ruby; otherwise, the stone will be called a pink sapphire.
The color of ruby ranges from bright red to dark reddish-brown. The most preferred color is a deep blood red with a slightly bluish hue. Such ruby is known as "Burmese Ruby" or "Pigeon's Blood Ruby". Ruby from Burma is famous for its exceptional coloring and has traditionally produced the finest rubies. However, Burmese ruby rarely exceeds several carats; large flawless Burmese rubies can be worth millions of dollars. Many rubies on the market are from Thailand, and these rubies have a less-desirable brownish hue, though they often can be heat treated to improve color.
Inclusions of tiny, slender, parallel rutile needles in ruby cause a polished gem to exhibit asterism. A ruby displaying asterism is known as a "Star Ruby", and if transparent can be very highly prized. Star rubies exists in six ray stars, though twelve ray stars are also known. Rubies must be having good transparency to possess gem value. Opaque or semi-opaque rubies have relatively little value, even if they display asterism.
The same rutile inclusions that are responsible for asterism in certain rubies can also decrease transparency and cause a hazy effect known as silk. Though ruby can be one the most expensive gemstones, it also comes in duller opaque forms that are fairly inexpensive and are often polished into cabochons. A unique gemstone form composed of opaque red ruby in contrasting green Zoisite is well known from Tanzania and is used as a minor gemstone and can be carved into ornaments.
The color of ruby is usually caused by minute inclusions of the metal chromium. These impurities are often responsible for causing a ruby to fluorescent, which can be helpful in its identification. Ruby is also pleochroic and will sometimes display a lighter and more intense color when viewed at different angles.
Improving the quality of gemstones by treating them is common practice. Some treatments are used in almost all cases. Improvements used include color alteration, improving transparency by dissolving rutile inclusions, healing of fractures (cracks) or even completely filling them.
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.
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.
Ruby is a tough and durable gem, and the only natural gemstone harder than ruby is diamond. Despite this, ruby is still subject to chipping and fracture if handled roughly, and care should be taken to ensure it is properly handled.
Ruby was first synthesized in 1902. The process of creating synthetic ruby is known as the Verneuil process. Only experts can distinguish between natural and synthetic, lab-created ruby.
Ruby is a powerful stone to shield against negative energy, psychic attack, and energy vampirism, especially of the heart energy. Working with Ruby one may feel that all sense of limitation has been removed, strengthening courage, joy, leadership qualities and selfless work in all spiritual endeavors.
It is an excellent stone for recharging your energy levels, and it may stimulate your mind to be more positive and self-assured. Its striking color is analogous of its energy, which is very effective for encouraging vitality, sensuality and sexual energy.
Ruby helps eliminate signs of fatigue and depression, and also helps the blood circulation, promotes blood cells formation, and purifies the blood and lymph. It regulates the function of the liver and spleen and stimulates the adrenal glands and kidneys.