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Sapphire fact file | |
Crystal Structure: hexagonal Chemical Composition: Corundum ( Aluminum oxide- Al203 ) Hardness: 9 MOHS | Refractive Index: 1.762 to 1.77 Colors: yellow, green, pink, clear, and blue |
Sapphire, the symbol of truth, is the September birthstone. This blue, celestial gemstone is the chemical cousin of ruby, having the same chemical composition – corundum.
Star sapphires and rubies display a six-ray star that moves across the face of the gems when light hits the stones. The star is created by intersecting lines of the mineral rutile that form symmetrically in the gem.
Name
The name sapphire derives from the Latin form of the Greek word for blue, sapphirus.
Physical and Chemical Properties
Chemical composition
Sapphire is a variety of corundum or aluminum oxide and Al203 gives its chemical formula—that is, two parts of Aluminum to three parts of Oxygen. Except for color, all of the other physical and optical properties of sapphire are identical to those of ruby.
Colors
The colors of sapphires and rubies are controlled by trace elements that are included in the crystal lattice in amounts usually not exceeding about three percent. Some of these are:
- Chromium Oxide, Cr203—–ruby
- Titanium Oxide, TiO2 and Ferrous Iron Oxide, Fe203—–blue
- Ferrous Iron Oxide—–yellow
- Chromium Oxide, Ferrous Iron Oxide—–Orange
- Ferric Iron Oxide, Fe304 and Titanium Oxide—–Green
- Chromium Oxide, Ferrous Iron Oxide, Titanium Oxide—–purple
Sapphires can be found in a wide range of colors, such as yellow, green, pink, clear, and most famously, blue; all red corundums are considered rubies. There are many shades possible for blue sapphires, ranging from light clear blue to inky blue-black stones. The most valuable color is called “cornflower” blue. Some sapphires displays streaks of a lighter color that contrast with the darker base.
Healing Properties and Interesting Information
Where Found
Cornflower blue sapphires are rare and the finest examples come from Kashmir, a mountainous area in northern India on the Pakistan border. Geographic isolation, political instability and high demand all combines to make these september birthstones very expensive. Sapphires have been found in many other places in the world but few have attained the desirability of the Kashmir stones. In the United States, the Yogo Gulch area in Montana has historically produced some fine sapphires. In the Old World sapphire has been found in alluvial gravel in Burma and Sri Lanka. Many of the colorless stones from Sri Lanka can be enhanced by heat treatment. There are many other localities of lesser importance throughout the world that have produced sapphires. corundum forms in two distinct geochemical environments. (1) Alkali basalt where partial melting of the lithosphere over rising plumes of the earth’s mantle can lead to eruptions of gem bearing lava. (2) Sapphires from Montana formed in crustal metamorphic sources on the basis of low Gallium contents. Sapphire form in rocks that geologists call undersaturated, or rocks that have no free quartz. Spinel is another gem that forms in undersaturated rocks. The most valuable blue sapphires come from Kashmir, India. Sri Lanka provides sapphires that are clear, pink, green, and yellow. Other sources include Myanmar, Australia, Nigeria, and Thailand as well as the Yogo Gulch Mine in Montana.
History, mythology
An ancient Persian legend says the earth rests on a giant sapphire and the blue of the sky comes from the gem’s reflection. During the Middle Ages, sapphire symbolized the tranquility of the heavens, and wearing it was thought to bring peace, happiness, and purity of the soul. Medieval priests and monks would wear sapphire jewelry believing it had the ability to quell wicked impulses and impure thoughts.
Buying and Caring tips
Tips for Buying Sapphire Jewelry
For a one-carat stone of average-to-good quality you can expect to pay between $250 and $10,000 per carat. Spinel may come in many of the same colors as sapphire and in earlier times many stones that were called sapphire or ruby included both corundum and spinel. Modern gem testing procedures can easily separate the two different minerals. Supply and demand has dictated that cornflower blue sapphires are the most expensive.
Tips to take care of Sapphire Jewelry
Clean with soapy water or commercial solvent and brush. Mechanical cleaners are safe, except for heavily included gems.