Gemstone clarity refers to the degree to which inclusions (tiny imperfections) are present. The occurrence, type, and acceptability of inclusions varies from gemstone to gemstone. Emerald, for instance, tends to contain visible inclusions and can still be valued highly despite this.
Unlike for diamonds, there is no standard grading scale for colored gemstones. Fewer flaws generally translates to higher prices, though there are some cases in which specific flaws actually increase value. One example of this are horsetail inclusion in green demantoid garnet.
The clarity of a colored gem must be compared to what is standard for that variety. Aquamarine, for instance, naturally tends to contain fewer inclusions than ruby.
A diamonds are graded for clarity under a 10X microscope and an expert human eye. Gemstones that have no inclusions or blemishes would be regarded as FL or flawless. The scale has 11 ratings going down to I3, which means that there are several inclusions which will be visible to the naked eye.
Jewellers will use the 4Cs to judge the quality of a gemstone and these stand for: Carat Weight, Cut, Colour and Clarity. Obviously, the higher the clarity, the better the cut and the clearer the colour; the higher quality the stone. Carat Weight is important in terms of value, but a less important factor when it comes to quality.
It is generally accepted that the colour grade has more significance than the clarity when it comes to judging the quality of gemstones. Even SI1 and SI2 gems will have inclusions that are not visible to the naked eye, but the colour will be more obvious. Therefore, you should always choose the colour over clarity when selecting a gemstone such as a diamond.
The highest quality of gemstone would be given a “AAA” grading, and they would be described as “being near perfect”. They may show slight variations in colour, but they will have a higher clarity rating and be well cut and polished.