Grading Terms
"Colored stones grading" is used by the industry in general to establish a benchmark in comparing Faceted gemstones. It breaks down into many categories depending on: Color, Clarity, Cut,Carat.New Directions use a sliding scale from A to Gem for the grading of our gemstones. When you are comparing Cabochon gemstones there is no real establish grading. We have established a four-tier guideline for the grading of cabochons (See Cabochon Gemstones in the table below) from Cab A to Cab Gem. The scale is based in order on the following priority: Cut, Gem Material, Coloration, and Clarity (For additional information go to the bottom of this page).
Faceted Gemstones |
|
Scale |
Comments |
Gem |
Exceptional quality - internally flawless, meaning that the stone was examined under a microscope of at least 40x magnification and no inclusions were seen. The stone has rich color with vivid saturation and an outstanding cut. |
AAA+ |
Outstanding quality - loupe cleanmeaning that no inclusions are seen using 10x magnification. There is great color with strong saturation and an outstanding cut. |
AAA |
Excellent quality - loupe cleanmeaning that no inclusions were seen using 10x magnification. The stone has great color with moderately strongsaturation and an outstanding cut. |
AA+ |
Good quality - very slightly included, meaning that the stone has some minor inclusions which are difficult to see by eye. The stone has good color and a good cut. |
AA |
Fair to good quality - possible minor inclusions, meaning that the stone may have visible inclusions. The stone has good color and a good cut. |
A+ |
Average quality - included, meaning that the stone has visible inclusions. Color and/or cut may be fair but would setup well. |
A |
Below average quality - moderately included, meaning that the stone is transparent, but there are several inclusions, which are visible without magnification. Inclusions, color, and/or cut deviations should not impair use for many projects or setting. |
Gemstones of lower quality are not listed here and are not in our inventory unless otherwise identified. | |
Cabochon Gemstones |
|
Scale | Comments |
Cab Gem |
1. Is expertly and uniformly cut 2. Displays a top example of the material’s primary attribute, whatever that may be. 3. Displays coloration distinctive and exemplary of the material. 4. Has excellent clarity, whether it be of a uniform opaquity, or crystalline in nature |
Cab AAA | 1. Is expertly and uniformly cut (as this is the #1 consideration in a cabochon stone) 2. Is lacking slightly in any one other attribute. |
Cab AA | 1. Does not meet the cutting requirements for Cab GEM. -or- 2. Is lacking slightly in two other attributes. |
Cab A | Lacking in two or more attributes including cutting, yet still pleasing to the eye and suitable for using in jewelry. |
Cabochon Grading
First, in order of priority, these are the
things to consider in grading cab materials (as well as facet materials that
have been cabbed).
1.Because of the primarily non-optical properties
of most cabbing materials, the cut is of top importance.It should be either an even, uniform dome
following a single arc from one edge to another, or perfectly flat.If the material is a faceted cabochon or a
rose cut, the faceting must hold to the same standards as typical GEM faceted
stones.The girdle edge must not be less
than 90 degrees (either a flat bottom with a vertical edge or a tapered edge)
to facilitate use in jewelry.The polish
must be as high as possible for the material as well as uniform in appearance.
2.Next
comes the quality of the primary attribute of the gem material, whether it be
asterism, chatoyancy, clarity, plechroism, or the primary attribute of its
inclusion, ie. well formed tourmaline needles, visible insect, symmetry of
rutile star burst.If it is an inclusive
attribute, it should be well centered or placed within a plane of symmetry of
the stone.
3.Coloration is third in materials which
coloration or an aspect of coloration is not the primary attribute.In dichroic or trichroic materials there
should be a clear distinction between colors.In monochromatic materials the color should be
even throughout the stone.
4.Clarity.In translucent cabochon materials clarity
usually comes into consideration only so far as uniformity is concerned.It refers to the homogenous level of opaquity
within the stone when lit from underneath.In
transparent cabochon materials the clarity is given the same considerations as
in a typically faceted stone.
Of course there are some exceptions, but this applies to the vast majority of materials. The major exceptions are stones such as druzy materials in which cutting takes virtually no part, and stones such as fire agate where coloration and polish, not cutting is top on the list.