Blue Spinel is a very special gemstone because it is one of the few that occur naturally. While all Spinels are increasing in popularity, it is the blue variety that is starting to attract attention of savvy gemstone buyers. Unlike the other blue gemstones such as Sapphire, Tanzanite and Aquamarine, there is no known treatments for Spinel. This means that every Spinel is completely natural and free from any modifications by man.
Spinel for many years has gone unnoticed as a gemstone if great durability and intense color. In recent years the famous red and vivid pink Spinels from Mahenge, Tanzania and Burma have had all of the glory of the beauty of Spinel. Now people are starting to notice the more pastel colors including the beautiful blue Spinel.
The blue Spinel is colored from the impurity of Cobalt in the crystal lattice. These stones are commonly referred to as Cobalt Blue Spinel. In many locations such as Sri Lanka, the Spinel will have a high iron content which tends to make the stones darker. This makes the stones look blue-gray to violet-blue in color instead of just the pure blue.
If the blue Spinel has a high iron content and looks dark in color, it is best viewed in daylight (Specifically sky light where the sun comes from over your shoulder and you cast a shadow over the stone). This will bring out the bright sparkles of blue color in the blue Spinel.
Inside these stones tend to be dark and less lively than outside.
Like all Spinel these stones should be eye clean and free from inclusions. If the stone has visible flaws it will reduce the price.
The more vibrant the color the higher the price will be. High saturation in color with a medium tone are the most expensive type of blue Spinel. These are always colored by Cobalt and are extremely rare to find.
The Chelsea Filter is a tool that shows traces of Chromium and Cobalt. When a natural Cobalt blue Spinel is viewed through the Chelsea filter it appears a bright red color. Spinel that does not contain Cobalt will not turn red.
With modern gemological tools we can easily distinguish between Blue Spinel and Blue Sapphire. However hundreds of years ago when Spinel was found together with Sapphire and Ruby it was impossible to tell them apart. There is no telling how many Spinels have actually been sold as Sapphire.
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