How Color in Gemstones is Assessed

Gemstones, like diamonds, are graded based on the 4Cs, color, clarity, cut, and carat. This may come as a surprise to some, since most gemstones are quite different than diamonds, but the truth is, at the end of the day, diamonds are precious gems as well. They just happen to be in a league of their own.


Gemstones are assessed differently within each category, and this is due to the difference in color, texture, and other qualities. The color aspect takes precedence over the three remaining characteristics.  This is essentially because the color is what sets it apart from other stones and what catches the eye the most. However, the other attributes play an important role as well.


Assessing Color in Gemstones


In order to assess the color of a gemstone, there are three categories to bear in mind. There is the stone’s hue, which indicates the color, its saturation, which is the level of gray mixed in with the color, and lastly, the tone.


Hue – A stone’s hue can be a pure primary color (red, blue, or yellow) or a secondary color, which is the result of primary colors mixing (orange, green, and purple.) A stone’s color can also be mixed with gray, white, or black, which results in the need for yet another grade. When there is gray in a stone, it is the saturation that needs to be graded. When there is white in a stone, it is the tint that needs to be defined. The presence of black in a stone can affect the tone. Most stones are more valuable when there is little tint, though there are some exceptions.


Saturation – The presence of gray in a stone contributes to the saturation level. It is less desirable for a stone to contain gray in it, therefore the less there is of the gray the higher the saturation. A stone with zero gray presence, which would in theory receive a 100% saturation grade, has never been found.


Tone – The amount of black or white color mixed into the primary color is what determines the tone of a gemstone. A stone will have a dark tone if there is a high percentage of black mixed in. A stone will be very light if there is white mixed in. A stone should not be too dark that you cannot tell what color it is, nor should it be too faint. That is why on the tone grading scale, the middle grades of medium-dark, medium, and light medium fetch the highest prices. Dark, Light, and Very Light tone gemstones are far less valuable. However, a stone is never graded based on its tone alone. It is the tone combined with the stone’s color that determines its worth.


A stone can potentially be pure, and free of other hues but it is never free of grey, white or black, and can therefore never receive the highest color grade. But the stone is not based on color alone, but rather, also on its tone. Color grades run 1 through 10. 1-2 is excellent, 3-4 is very good, 4-5 is good, 6-7 is fair, 8-9 is poor, and 9-10 is very poor. Gemstones must be in the 1-4 range with a Medium-Dark to Light –Medium tone to be considered high quality gemstones in terms of color.


Clarity in Gemstones


The clarity in gemstones refers to the amount of inclusions in the stone. A gemstone that is Free of Inclusions is a stone that has inclusions that even under 10x magnification cannot be seen. Very Lightly Included stones may or may not have inclusions that can be detected by a professional with a lens. Lightly Included gems have inclusions that are detectable under 10x magnification, but not often with the unaided eye. Moderately Included stones possess inclusions that the naked eye can see but they do not dominate the gem.  Heavily Included and Excessively Included stones have clear and visible inclusions that affect the stone’s appearance and in the case of the latter, the stones may not be durable.


Part of a stone’s clarity is the brilliance it displays. This is related mostly to the way in which the stone was cut. The depth of a stone is another aspect of gemstones and is related to clarity as well. The height of the stone divided by its minimum width is a stone’s depth. Ideally this should be between 60% and 80%, however this depends greatly on the rough shape of the gem. Stones that are under 50% are considered shallow and may find it hard to maintain saturation. On the other hand, stones over 90% might blackout if it has a dark tone.


Cutting Grades for Gemstones


The cutting grade for gemstones is just part of the overall grade it receives. The cutting grade is comprised of both the diamond’s brilliance and the diamond’s depth. The grade also includes the general quality and precision of the diamond’s cut and finish. If the cut has any flaws or weaknesses it will be mentioned in this grade. Though it is possible to look at the individual great for each and every aspect, you can keep it simple and look at the overall grade, which summarizes all of the diamond cut’s elements. This grade consists of five levels. These are Excellent, Very Good, Good, Fair, and Poor. Statistics show that 900 out of 1000 diamonds mined will fall into the Fair or Poor categories, while only 1 will receive the Excellent grade.


Gemstone Carat Weight


People would generally assume that the bigger the better, and therefore more expensive. However, with gemstones, it is not so black and white. Though many times larger stones are more sought after and therefore far pricier than smaller stones, this isn’t always the case. There are some gemstones such as the ruby, which are often found in large sizes. However, it is extremely difficult to come across a ruby with high clarity. Therefore, a much smaller ruby with few inclusions will cost a pretty penny. Additionally, a stone’s weight does not necessarily reflect its visual appearance. What this means is that a rather heavy stone may be very deep, and much of its weight will not be seen when set in a jewelry setting. On the other hand, a much lighter stone could appear much larger simply because it is shallow but wide. Someone with a tight budget could benefit greatly from such a stone.


Nature has left us with many different types of gemstones, each with its own unique features. There are many aspects of a gemstone that need to be examined in order to assess its true worth. However, there are many different laboratories that produce these stones, and some have different grading systems. Additionally, each and every person has different taste. If it is a matter of selecting a gemstone for a jewelry piece, then one should go with the stone that speaks out to him or her. After all, beauty is in the eye of the beholder.

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