Like many stones, the per-carat price of fine quality emerald escalates rapidly with size. For example, a recent price guide lists a fine quality 3-ct Colombian stone as six times more valuable than three equivalent quality 1-ct stones.
Value factors hinge largely on color, with nuances of saturation and hue affecting price to a significant degree. The most desirable color is a slightly bluish green in a medium dark tone with strong to vivid saturation.
Color: Vibrant green
Refractive Index: 1.577 to 1.583
Birefringence: 0.005 to 0.009
Specific Gravity: 2.72
Mohs Hardness: 7.5 to 8