Our grading scale consists of six judgments of color, cut, clarity and rarity of the gem. The overall grade is an easy way to quickly gauge and compare against other gems in our collection.
HISTORY OF GEMSTONE GRADING
Before explaining our grading system, it is important to learn a brief history of gemstone grading. Unlike diamond grading, where there are uniformed grading standards created by the GIA, color gemstones don’t have a consistent scale. Numerous gemological organizations have attempted to create a scale—but the problem is they are never universally adopted by the marketplace. As such, we’ve picked and chosen what we believe is the best elements of grading that can be readily understood by the novice as well as the expert.
This is our way of summarizing the information into an easy to understand scale—from 1 to 10 (10 being the best). Generally, stones with a 9-10 overall grade are of exceptional quality and exceedingly rare. In fact, we don’t have any stones that we have graded as a 10 – we like to err on the strict side of our grading. Grades of 7-8 are great stones. An overall grade of 4-6 is fair. And an overall grade of 1-3 is a poor grade. What grade is right for you? This is going to depend on many factors including your budget, and your preferences in terms of quality (for example, do you prefer having a clean stone with a window over an included stone with a superb cut?) All of the elements that make up the overall grade, are graded on a scale of 1-5.
This is our grade for the quality of the color. This is based on not only if there are issues with the color in terms of color banding, but also the level of desirability of the color. The most desirable color for the peridot would be a vivid apple green color without brown undertones.
This is our judgment on the symmetry of the shape of the stone. If a round stone is not perfectly round, then it would be lacking in symmetry. If a pear shape is not equal on both sides, it would be lopsided and not symmetrical. While no gemstone is perfectly symmetrical, we are able to grade the symmetry on a scale of 1-5 (5 being the best).
POLISH & FINISH
The polish and the finish is grading the smoothness of the facets, as well as the facet junctions (straight, meeting at points). We look for obvious problems such as chipping and abraded facets which will result in a lower grade for polish. We grade on a scale of 1-5 (5 being the best).
The window is best demonstrated visually. These are links to two stones, one with a big window, and one without a window. In summary, a window allows light to pass out the back of the stone without reflecting back up through the face. It is easy to see a window, because you can see right through the stone and out the back. A window is only judged from the face-up position. As a gem is tilted, a window will become obvious based on the degree of the tilt. Even an ideal cut diamond will show a window when tilted to the right degree. That is why it is important to grade the window only from the face up position.
Clarity grade assesses the internal inclusions of the gemstone. Inclusions may be other minerals that were trapped as the peridot crystal was growing. Chrome Diopside commonly possesses a bubble type of inclusion which is not visually offensive. We grade our clarity on a scale of 1-5, 5 being the best (we call this very very lightly included). Why don’t we have an internally flawless grade? Well, let’s face it—at 10x magnification we can find a flaw in almost anything. Some people may grade clarity for color gemstones without magnification. You must be aware of each vendors clarity scale as there is no universal standard for color gemstones.
Rarity is a very subjective grade. All gemstone grading is subjective (to some degree)—rarity is very subjective. We base the grade of rarity on our knowledge of the gemstone market and our own availability. For a general rule of thumb: the larger the chrome diopside, the more rare it will be.