Friday, May 3, 2013

Gemstone Love: Sapphires!

I love gemstones!  I've been collecting gemstones (loose ones as well as in jewelry) since I was about 16.  I used to LOVE going to the "Hall of Gems" at the Field Museum in Chicago.  I'd spend a huge amount of time staring in the cases, amazed at the colors and beauty of the gems.  I think my favorite was the Aquamarine---what a color!  They had a faceted Aquamarine the size of my fist, and that soft ocean blue-green color....WOW. 

Anyway, sapphires are such wonderful stones.  When you think of sapphires, most people think of the rich blue stones (like Kate Middleton's ring).  But sapphires come in every color of the rainbow, including clear, grey and black!  Here are some interesting facts about sapphires:

 - Sapphire is the gemstone variety of the mineral Corundum.
 - When a sapphire is red, it is called a RUBY!
 - Colorless (white) sapphires are often used as diamond substitutes.
 - Sapphires are VERY hard, rated a 9 on the Mohs scale, and only a diamond can scratch it!
 - Sapphires are so hard that they are used in scientific instruments, watch crystals, and for many other scientific and practical uses.
 - A sapphire, when it is a certain shade of pink-orange, is called Padparadscha.
 - Sapphires are found all over the world, including Montana.

Regarding colors:

Rainbow Sapphires - ring in my shop!
Color in gemstones breaks down into three components: hue, saturation and tone. Hue is most commonly understood as the COLOR of the gemstone. Saturation refers to the vividness or brightness of the color, and tone is the lightness to darkness of the color. Blue sapphire exists in various mixtures of its primary (blue) and secondary hues, various shades, and at various levels of saturation (vividness).

Blue sapphires are evaluated based upon the purity of their primary hue:  purple, violet and green are the most common secondary hues found in blue sapphires. Blue sapphires with up to 15% violet or purple are generally said to be of fine quality.

"Fancy Sapphires" - when sapphires are found in other colors (other than blue), they are called "Fancy" sapphires.  Pink Sapphires are very valuable when they are very deep pink, almost red in color.

Color Change Sapphires - very rare, exhibits different colors in different lights.  Sometimes these are sold as "created Alexandrite" but they are neither created nor alexandrite!

It's common for sapphires to be heat-treated to enhance color.  This is done by heating the sapphires in furnaces to temperatures between 500 and 1800 °C for several hours, or by heating in a nitrogen-deficient atmosphere oven for seven days or more. Once heated, the stone becomes more blue in color but the stone loses all silk (inclusions) and it becomes clear under magnification.

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