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January 18, 2015



Color, Clarity, Cut and Carat, are the four famous  “C’s”.

We need to take into account what it is that we intend to describe with the 4 C’s: A diamonds or a colored gemstones?


Regarding diamonds, their classification and graduation follow clear rules, and for those who want to research and enjoy, I recommend the following basic book where you will find information about diamond grading: DIAMOND GRADING ABC THE MANUAL. Verena Pagel – Theisen. 


However, this is a shop for colored gemstones.

For gemstone grading there are no set rules that are as clear as those for diamonds, and there is NOT a standard classification for clarity in colored gems.


The GIA (Gemological Institute of America) has provided a classification to address both color and clarity issues, and that is what I use here (I know this is a controversial subject, but I think this classification is, for the moment, the most universal)




The COLOR factor is decisive for the price of a colored gemstone. It greatly affects its value, as gemstones with intense, bright colors, with a good saturation, will be the most expensive.


The same gemstone can show a different look depending on the light (day or night light, incandescent, fluorescent, etc.)


We can also find bicolor gemstones, or gemstones with asterism, chatoyant stones (cat's eye effect), changes of color, like alexandrites for example, that change color from green to red depending on the type of light they are exposed to, etc.


For a better understanding of color, it is necessary to go through some general concepts (again we will use GIA's values):




Base color,  the dominant or main color of the gemstones. (They can have a secondary color).

We will use the following base colors:



red /rojo


orangey red / rojo anaranjado


red orange ó orange red rojo naranja ó naranja rojo


reddish orange / naranja rojizo


orange / naranja


yellowish orange / naranja amarillento


orangey yellow / amarillo anaranjado


yellow / amarillo


greenish yellow / amarillo verdoso


yellow green/green yellow amarillo verde/verde amarillo


strongly yellowish green verde fuertemente amarillento


yellowish green / verde amarillento


slightly yellowish green /  verde ligeramente amarillento


green / verde


very slightly bluish green / verde muy ligeramente azulado


bluish green (bG) / verde azulado


very strongly bluish green verde muy fuertemente azulado


green blue ó blue green / verde azul ó azul verde


very strongly greenish blue azul muy fuertemente verdoso


greenish blue / azul verdoso


very slightly greenish blue / azul muy ligeramente verdoso


blue / azul


violetish blue / azul violáceo


bluish violet / violeta azulado


violet / violeta


violetish purple púrpura violáceo


purple /púrpura


redish purple / púrpura rojizo


purple red ó red purple /púrpura rojo ó rojo púrpura


strongly purplish red / rojo muy fuertemente purpura


slightly purplish red / rojo ligeramente purpura





The Tone is the grade of darkness or clarity of a color. The GIA sets 11 levels, from colorless to black, although in practice (as the eye cannot see the color extremes) only the following colors are used:











Very light


Medium light


Medium dark


Very dark





In gems there are certain shades that can be noticed, such as greys (cold colors) or browns (warm colors). The saturation level is set depending on the quantity of traces of browns or greys:  the higher the saturation the more beautiful a gemstone is.

A scale ranging from 1 to 7 is set. If the brownish or greyish shades are evident the saturation level will be 1 or 2, if they are hardly noticeable the level will be 3, and 4 or higher is given if there are no visible brown or grey traces.





brownish / grayish


slightly brownish / grayish


very slightly brownish / grayish


moderately strong






Extremely vivid



And even with all these tools and data, there are occasions when it is hard to describe a gem's color. But the general idea to be deducted from all this information is that in the world of colored gemstones, COLOR is the most important quality.


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