The most important factor in the value of a ruby is color.
The best qualities of ruby can be as red as you can imagine: a saturated pure spectral hue without any overtones of brown or blue. The intensity of color of a fine ruby is like that of glowing coal.
After color, the other factors which influence the value of a ruby are size, clarity and cut. Larger rubies, because they are rare, will cost more per carat than smaller stones of the same quality. Sizes above five carats are particularly rare.
Rubies that are perfectly transparent, with no flaws, are more valuable than those with inclusions which are visible to the eye.
The cut can make a big difference in how attractive and lively a ruby appears to the eye.
The shape should also be symmetrical and there should not be any nicks or any scratches in the polish.
Ruby sometimes displays a three-ray, six-point star. These star rubies are cut in a smooth domed cabochon cut to display the effect. The star is best visible when illuminated with a single light source: it moves across the stone as the light moves. This effect, called asterism, is caused by light reflecting off tiny rutile needles, called "silk," which are oriented along the crystal faces.
The value of star rubies and sapphires are influenced by two things: the intensity and attractiveness of the body color and the strength and sharpness of the star.
Consult list of gems available on the Chanthaburi market...
Consult list of gems available on the Jaipur market...