Ruby can command the highest prices of any colored gemstone. The per-carat prices of fine-quality rubies have been rising consistently, many times breaking auction records.
For better-quality material, slight differences in color can make significant differences in value. For top-color ruby that’s also free of eye-visible inclusions, the price rises even more.
The per-carat price of ruby can also increase dramatically as size increases, especially for better-quality stones.
Color is the most significant factor affecting a ruby’s value. The finest ruby has a pure, vibrant red to slightly purplish red color. As the color becomes too orangy or more purplish, the ruby moves down the quality scale. The highest-quality rubies have vivid color saturation.
The color must be neither too dark nor too light to be considered finest quality. If the color is too dark it has a negative effect on the stone’s brightness. At the other extreme, if the color is too light, the stone is considered pink sapphire, even if color strength or intensity is high.
Some gem dealers debate the borderline between ruby and pink sapphire. Historically, the word ruby referred to shades of red, which technically included pink. There are also cultural differences in the interpretation of ruby versus pink sapphire. In some gem-producing nations such as Sri Lanka, pink colors were always considered ruby, while in many consuming countries it is classified as pink sapphire.