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Grading and Valuing Ammolite

Each piece of ammolite is a unique and individualistic piece of art created by Mother Nature. No other gemstone has the range of colors and patterns that can be found in ammolite. Ammolite earrings can be a rare commodity just because it is so hard to find 2 pieces of ammolite that match well enough to create earrings. Grading ammolite is therefore a very subjective exercise. To place a value on each unique stone, the grader has to tie together -

~ How reflective/brilliant is the stone?
~ How many colors appear in the stone?
~ How pleasing is the pattern?
~ Do inclusions or other flaws add to or detract from the pattern?
~ Is it too directional for the intended use?


The following discussion is in 4 sections.You can scroll through the information, or use one of the following links to go to a specific item. Simply page back up if you wish to return to the top of this page.


Traditional Grading
Practical Grading
Good - Better - Best
Carat Pricing

Traditional Grading
Ammolite is traditionally classified by letter grades. Jewelry is usually created from the A range grades. Normally, the higher the grade, the more brilliant the colors and the more the colors remain bright as the stone is turned in different directions.

I don’t believe an actual official grading system that is accepted by all of the various players in the "ammolite industry" currently exists - although I believe there are representatives from several groups working on one. Korite, the largest producer of ammolite, uses a letter grading system. Various sources of ammolite seem to follow this system - although they may define the grades slightly differently. The following kind of mushes together and averages out what I have found many different sources to say about how they grade ammolite:


AA the best stones, displaying brilliant multidirectional fire with a good
representation of at least three brilliant vivid colors. Colors are sharp &
clear, with crisp distinctions.

A+ at least two very bright vivid colors with little or no directional

A strong fire of one or more bright vivid colors that show from many

A- "standard" grade with good color. Colors either might not be as vivid as
the higher grades or they may be more prone to directional extinction.

B colors are not sharp and clear and may even be muddy. The stone just
is no where near as flashy as the A range grades and are usually much
more prone to directional extinction, becoming completely dark at many

C dark at most angles


Practical Grading
In practice, grading is a subjective exercise that tries to balance many factors and may not fit neatly into one of the above letter grades. Many people seem to focus on number of colors when selecting a grade. Personally, I feel that the brilliance of the stone is the more important factor when selecting a grade. In looking at a stone:


~ Are the colors clear and vivid? Are they brilliant or bright?
     (reflective intensity)
~ How many colors are present?
~ Is the pattern and color pleasing?
~ Do natural inclusions and/or black lines add or detract from the stone?
~ Does it have Flash? Depth? Life?
~ How common or rare is the color and/or pattern?
     (rare colors such as blue, purple, and pink are allowed more color
      extinction and flaws than other colors at the same grade level)
~ Do the colors change/shift as the stone is rotated?
     (red -> green, blue -> orange, etc - a good thing)
~ Do the colors extinguish (go dark) or become less intense as the stone
     is rotated?(directionality - a bad thing)
~ Are there flaws?
     (cracks in the stone that impact its stability, surface cracks, bubbles
      under the cap, poor polishing or poor finishing, etc)


Ammolite is a product of Mother Nature. You often find "inclusions" in ammolite - some detract from the pattern and some add to the pattern. The pattern can be as much of a factor in the value of a stone as the color.

Ammolite is found in all of the spectral colors plus purple. Greens and reds are the most common colors. Vivid blues and purples are highly prized and highly priced. Rare colors such as pinks may be pricey even when of lower quality because of their rarity.

Light plays an important role in the appearance of ammolite at any given moment. The light source, angle of the light, and the angle at which you are viewing the stone will all impact on the colors you see. I always find it amazing that rooms that seem darkly lit - especially restaurants with small intense spotlights over the tables - often give ammolite a completely different flash. The colors just seem to get much richer to me in that light.

The above factors also influence color shifts. A lot of ammolite does not display any chromatic shifts, some display only subtle changes, and some are totally spectacular. Color shifts are classed by the number of colors that show -
~ Monochromatic - the color changes between various hues of one color
~ Dichromatic - the color shifts between two different colors, for example,
     red becomes green
~ Spectrochromatic - as you play with the stone, the color can shift through
     the entire rainbow

Directionality (how much color is lost as the stone is turned in different directions) is due to organic inclusions in the aragonite that block light wave diffraction. Directionality occurs to some extent in most ammolite. If you like the stone, first consider whether the directionality impacts the intended use. For example, a directional stone may actually increase the "play" factor in a ring or bracelet, but would not work well in a pendant. I find a lot of stones that have a lot of color laying down go very dark when held upright, as they would be when worn as a pendant.

Ammolite is a natural stone produced by Mother Nature. It has inclusions - whether they be small surface pits, mineral inclusions, black lines, shell fractures, or something else. Inclusions can add beauty and character to a natural stone, or they can interupt the mirror surface of a triplet. Because the purpose of triplets often is to take the thinnest possible slices of the best sheet ammolite, to make as many stones as possible from the material, you don’t expect to see as many fractures or inclusions in them. They are valued more for their mirror like appearance than for their depth of character. Natural stones on the other hand are often given more depth of character by their inclusions. It comes down to a matter of what you like best. If it matters to you, it is important to look at the pictures carefully, to spot inclusions that may be present.


Good - Better - Best
Because ammolite grading is so subjective and because most stones I buy are not graded, I have decided to use a good/better/best system. (If less than "good", I don’t use it.) When I first get the stone, I play with it to see what type of jewelry I think will best show it off. After I have made it into jewelry, I again play with it, putting it in different lights and taking pictures. At that point, I assign it to a good, better, or best page based on how it reacts in the setting it has been placed in.

I am not following the traditional letter grading exactly. For instance, an A+ or AA requires multiple colors. I think brilliance is more important than the number of colors however, and if I have a stone that is an outstanding example of one color, it may go on the best page.

As with so many things, if you like it, that is the one you should buy, regardless of the grade.

Carat Pricing
For the most part, I don’t think about ammolite in terms of the price per carat, primarily because the weight of the stone depends so much on how much shale backing has been left on it. Since most of my stones are naturals and capped naturals, I focus my value decisions on the quality and visual appearance of the gem layer, and to some extent the amount of surface area. For "manufactured" stones like triplets and un-capped doublets, where the depth of the backing can be easily controlled, pricing by carats can make sense. The guideline I have heard for purchasing by carats is that the backing should not exceed 1.5 mm in thickness.

Continue Reading

Ammolite Jewelry - Good ~ Ammolite Jewelry - Better ~ Ammolite Jewelry - Best
Ammonite Fossil Jewelry
to see jewelry for sale.

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