Sapphire Gem Grades:
Sapphires are closely related to Ruby's having the same mineral and chemical composition from the extremely hard mineral corundum. Impurities of trace elements decide if the gem will be a red ruby or a blue sapphire. The best color for a natural blue sapphire is an intense, velvety, deep royal blue.
Most of the worlds highest quality sapphires are mined in Kashmir, Burma and Sri Lanka. But sapphires of varying quality are also found in places like Madagascar, Australia, Thailand, Vietnam, China, Kenya, Tanzania and even the United States.

Grades:
While there is no official grading system, most dealers use the 'A' scale for precious sapphires. Generally graded from 'AAA' to 'B', and on a blue colour scale
(see pictures below).The three keys to grading are the hue, tone and saturation of the sapphire. To qualify as an AAA blue sapphire, the hue should be velvety blue, the tone a deep blue and saturation even throughout the sapphire.

Sapphire gems can sometimes be found in several natural unique colour's. Pink, Green, Purple, Orange and Yellow.
The yellow or pink Sapphire is very sought after for its clarity and beauty and often found in the more exclusive jewellery. Yellow sapphires represent money and good judgment also mystically symbolizes the planet Jupiter.
Cornflower blue and orange-pink Padparadscha (displays different colors depending on its lighting) are much rarer and valuable if of high quality hue and brilliance.

A genuine blue Sapphire can cost trade price 500.00 per carat for a good AA/AAA stone. And 1000's for one of exceptional AAA+ quality.
There are several variations to the bluishness color of these gems as following blue colour scale shows.