Gemstone Color
By admin

Gemstone color is mainly determined by the elements that make up the stone. For example, the mineral species beryl has a complex chemical formula that includes the elements beryllium, aluminum, silicon, and oxygen [ Be3Al2(SiO3)6 ] If trace amounts of the aluminum in the crystal is replaced by chromium or vanadium, the resulting green variety is called emerald. If some iron (Fe+2) ions are present, the resulting bluish variety is called aquamarine. If the stone has other iron (Fe+3) ions the stone is yellow or yellowish-green and is called golden beryl or heliodor. Instead of iron ions if the stone has manganese (Mn+2) ions then the resulting pink colored beryl variety is called morganite. As you can see, very small changes in the chemistry of a rock can certainly make a big difference in its appearance!

Beryl (from left to right: Heliodor, Morganite, Aquamarine, Emerald)

In any individual gemstone mineral species, there is a preferred and more valuable color. This is primarily related to the rarity of one particular color relative to another. For example, emerald is far more valuable than aquamarine even though they are the same gemstone species (beryl).

Further, in a given gemstone variety there is also a preferred color. In the variety emerald, approximately 50% of the retail value is solely determined by the color of the stone. Emerald is classified into at least seven shades of green, each with a different base value. The value of a cut one-carat emerald gemstone may jump from $800 to more than $3000 solely based on the color of the stone. This same dependence of value on color is seen in most gemstone species and their varieties.

Green colors for evaluating emeralds. Each color has a base dollar value for emerald, with the value decreasing toward the right.

Evaluation of Gemstone Color

Anyone grading a stone may have a bias on color depending on whether they are buying or selling the stone. Even when not considering value, no two people are apt to see the color in exactly the same way. To further complicate this, stones may have areas of darker or lighter coloration, inclusions that change the light, and even multiple colors in the same stone.

It is in everyone’s best interest to objectively evaluate the color of a given stone, however, in the end, it is the buyer and seller agreement on price that determines the value.

There is no single internationally recognized authority for colored gemstone color-grading as there is for diamonds. Nevertheless, there is one industry-recognized color-grading system that we use at RSA Gems to color-grade our stones, both rough and cut.

World of Color Grading System

Gemworld International has created a gemstone color-grading system based on the Munsell Color System that has been in use throughout the world for many years. Their system is also tied to current industry data on value. The method is independent of the gemstone type – it works for all gemstones.

Additionally, the Gemological Institute of America has a color-grading system and is similar in many respects to the World of Color system and is equally effective. We try to report the color of our gemstones according to both systems, but our valuation is dependent on Gemworld International’s system.

Hue

Gemworld International has created a gemstone color-grading system based on the Munsell Color System that has been in use throughout the world for many years. Their system is also tied to current industry data on value. The method is independent of the gemstone type – it works for all gemstones.

Additionally, the Gemological Institute of America has a color-grading system and is similar in many respects to the World of Color system and is equally effective. We try to report the color of our gemstones according to both systems, but our valuation is dependent on Gemworld International’s system.

  • R — Red
  • YR — Yellow Red
  • Y — Yellow
  • GY — Green Yellow
  • G — Green
  • BG — Blue Green

Gemworld International has created a gemstone color-grading system based on the Munsell Color System that has been in use throughout the world for many years. Their system is also tied to current industry data on value. The method is independent of the gemstone type – it works for all gemstones.

Additionally, the Gemological Institute of America has a color-grading system and is similar in many respects to the World of Color system and is equally effective. We try to report the color of our gemstones according to both systems, but our valuation is dependent on Gemworld International’s system.

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