Ruby is red corundum, all other color varieties of corundum being referred to as sapphire. Corundum is the second hardest substance on the Mohs scale, with a rating of 9. Diamond tops the scale with a rating of 10. Excellent hardness combined with the rich color and silky shine makes fine ruby so valuable and secures them a position as one of the so-called “precious” gemstones.
Ruby is named after the Latin word “ruber” for red. Ruby is one of the most expensive gems, large rubies being rarer than comparable diamonds. Many rubies are an essential part of royal insignia and other famous jewelry.
Ruby crystal before faceting, length 0.8 inches (2 cm). Picture released to the public domain by Adrian Pingstone
Ruby is the birthstone for those who are born in July. Ruby is also used to celebrate a couple’s 15th and 40th anniversary.
Corundum: Corundum is best known for its gem varieties, Ruby and Sapphire. Ruby and Sapphire are scientifically the same mineral but just different colors. Ruby is the red variety, and Sapphire is the variety that encompasses all other colors, although the most popular and valued color of Sapphire is blue. Sapphire is also only used to describe the gem variety, otherwise it is simply called Corundum.
Corundum is a very hard, tough, and stable mineral. For all practical purposes, it is the hardest mineral after Diamond, making it the second hardest mineral. It is also unaffected by acids and most environments.
Ruby colors
Rubies range in color from pinkish to orangey and purplish and brownish red, depending on the chromium and iron content of the stone. The most desirable color is the so-called “pigeon’s blood”, a pure red with a hint of blue.
Buying Ruby
Color is the most important consideration, with clarity a distant second. Large rubies are rare.
Photo from Freedigitalphotos.net
Color
The most desirable color is the so-called “pigeon’s blood”, a pure red with a hint of blue. Color saturation makes all the difference.
Lighting
Ruby shows pleochroism which means that the color varies with the direction of viewing. Stones displaying the cat’s eye or star effect effect are best viewed in daylight.
Many rubies will fluoresce in long or short wave UV and this property can often be used to help identify a stone’s geographic origin. Burmese rubies often fluoresce so strongly that the effect is noticeable even in sunlight.
Such stones seem literally to glow. Thai rubies generally lack this property.
Clarity
Inclusions are common in ruby and not always an indication of lower quality. Included rutile needles cause the “silky shine”. If such a stone is cut en cabochon it exposes the rare cat’s eye effect. Oriented rutile crystal inclusions cause a six-rayed-star light effect (called asterism) to form the popular star ruby.
Ruby location and deposits
Myanmar: For centuries the most important deposits are in upper Myanmar (Burma) near Mogok. Only one percent of the production is of gem quality. Some of the rubies are of pigeon’s blood color and considered to be the most valuable rubies of all. In the early 1990’s large new deposits were discovered at Mong Hsu.
Thailand: Rubies found in Thailand (Chanthaburi district) often have a brown or violet tint. The Thai ruby production is declining, and Chanthaburi is now mainly a center for processing and trading gems.
Sri Lanka: The deposits are located in the southwest of the island in the Ratnapura district. Rubies from that deposits are usually light red to raspberry red.
Madagascar: in the 1990’s major ruby deposits were discovered in this huge island off the coast of Mozambique. Madagascar is now one of the world’s leading ruby producers.
Tanzania: On the upper Umba River in northwest Tanzania are deposits for gemstone quality rubies that are violet to brown-red. A few opaque rubies are mined as well.
Other deposits of some importance are found in: Afghanistan, Cambodia, Kenya and Vietnam. Less significant deposits are in: Australia, Brazil, India, Malawi, Nepal, Pakistan, United States and Zimbabwe.
Common Ruby treatments
The most common treatment for ruby is heat treatment. Stones, generally before they are cut, are heated to between 1700 to 1800 degrees Celsius (3100-3300 degrees F) for several hours. Heating often improves both color and clarity. A reputable dealer will always disclose gem treatments.
Lower grade rubies with surface-reaching fissures are often fracture-filled with lead glass.
This treatment produces good looking stones that can be sold at a very reasonable price.
World-famous Ruby
Famous stones of outstanding beauty and color are the “Edwardes Ruby”,weight 167 ct, displayed at the British Museum of Natural History in London, the “Rosser Reeves Star Ruby”, of 138.7 ct, to be seen at the Smithsonian Institution in Washington, the “De Long Star Ruby”, weight 100 ct, shown in the American Museum of Natural History in New York and the “Peace Ruby”, 43 ct, which was found in 1919.
Many rubies are an essential part of royal insignia and other famous jewelry. The Bohemian St. Wenzel’s Crown holds an unfaceted ruby of about 250 ct.
Information collected and compiled from The Mineral and Gemstone Kingdom, www.minerals.net and Wikipedia.
Sandra Kemppainen.
Exquisite, lustrous and gemmy ruby crystals in matrix, measuring up to 2 cm, together with small, blue crystals of kyanite. - wikipedia, user StrangerThanKindness
Bracelet with Ruby and Diamonds - wikipedia, paparutzi / christina rutz
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