The most valuable sapphires have a medium intense, vivid blue color. Any black, gray, or green overtones mixed in with the blue will reduce a stone's value.
In general, a more pastel blue would be less preferred to a vivid blue, but it would be priced higher than an over dark blackish blue color.
As with all gemstones, cut can affect greatly the visual appearance, and sapphires with good proportions and color balance and which have no or barely visible inclusions are the most valuable.
However, some very fine sapphires, in particular those from Cashmere, have a velvety mist-like texture which enhances the richness of the blue.
Other popular shades for sapphires are yellow, bright orange, lavender and purple, or a bluish green color.
Generally, the more clear and vivid the color, the more valuable the sapphire.
If the color is in the pastel range, because in lighter tones inclusions are more noticeable, for a better sapphire, the clarity should be good.
In a lighter colored gemstone, the cut is also more important: it should reflect light back evenly across the face of the stone, making it lively and brilliant.
With darker, more intense colors, the cut is not as critical because the color creates its own impact.
Sapphires with an unusual kind of tiny needle-like inclusions can be cut in a cabochon shape to display a dancing six-rayed white star.
As with rubies, star sapphires are judged by the sharpness of the star, the evenness of the rays or "legs" of the star, and the body color of the stone.
Sapphires have become more available in the past twenty years because some light, cloudy, or over dark sapphire can now be heated at very high temperatures to improve the color or clarity. This process, which dissolves trace elements already present in the sapphire, is completely stable.
There is no price difference between heated and non-heated material except for at the very top end of the market.
About 90 percent of the blue sapphire on the market today has been heated to make sure it has reached the best possible color and clarity.
Consult list of gems available on the Chanthaburi market...
Consult list of gems available on the Jaipur market...