How to Study Sapphires
Sapphires and rubies both come form the same mineral, known as corundum or natural aluminum oxide. When this mineral is found in any color other than red, it is called a "sapphire." Gemstones are assessed according to the four C's: color, clarity, cut and carat. Each stone and the mineral it comes from also have properties observable under good lighting conditions, using a powerful magnifying glass or a microscope.
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Instructions
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Observe the color of the stone. Whether it is raw or cut, sapphires can have a variety of tones. Aside from being blue, they can also be completely colorless, green, yellow or even a rare pink-orange color called padparadscha. Stones that turn a reddish or violet hue under artificial lighting are alexandrine or alexandrite sapphire. Sapphires that are not blue are always identified with the color first, such as yellow sapphire or green sapphire.
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Check the chemical composition according to the color of the stone. Blue stones are colored by trace titanium and iron, while pale green, yellow or brown stones contain iron and pink is created by a very small amount of chromium. A guide to minerals will be able to name other substances present in color variations.
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Take notes based on the clarity and consistency of the stone you have. If it is cut and polished, you will be able to check for any inconsistencies in color such as streaks or changes in tone. Use a powerful magnifying glass or a microscope of average strength. Sapphires have a range of lustre, varying from adamantine or very brilliant to vitreous, meaning glassy and low lustre. Some sapphires are even transparent, while others can be almost the opposite or translucent.
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Weigh the stone to find its value in carats. You may need a scale specifically designed for this purpose, because a carat is the equivalent of a fifth of a gram.
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Assess the cut of the stone according its visual brilliance, or how much light is reflected. A cut that reflects more light is a measure of how much time and skill the person who made the original gemstone dedicated to the stone. Sapphires cut and sanded into precise dome shapes, with cuts that are aligned perpendicular to the crystal formation lengthwise, create light reflections that form natural star shapes. These are highly-valued stones called "star stones." The Star of Bombay is a famous 182 carat sapphire from Sri Lanka kept at the Smithsonian Institute in Washington, D.C, which has a striking star reflection from the titanium oxide in the stone.
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Tips & Warnings
If you are estimating a price, be aware that rarity has the strongest effect on value, i.e. a ruby is rarer than a garnet and is worth much more.
References
- Photo Credit blue sapphire chain image by OMKAR A.V from Fotolia.com
