Unique, One-of-a-Kind Settings for Unique, One-of-a-Kind Stones
Ammolite Gem Stones
Ammolite ~~ Ammonite ~~ Unearthed ~~ Misc Info ~~ Gem Stones ~~ Lore ~~ Rockhounds
This page has a variety of information regarding ammolite gem stones.
Ammolite Patterns
Stone Types
Treatments
Care and Cleaning
Grading and Valuing
Ammolite Patterns
Ammolite patterns are created by the size and shape of the scales, the presence or absence of fractures and/or black lines, and colors. Pattern names are used fairly loosely and, to some extent, pattern name can be an individual preference. But the more ammolite you see, the more patterns you recognize.
Dragonskin - small scales, reminding one of the skin on a dragon or lizard
Checkerboard - larger, blockier pattern than dragonskin
Cobblestone - like the uneven, irregular appearance of a cobblestone street
Ribbon / Banded / Striped - colors run in wide to thin bands
Wave / Ripple - water surface ripples (or their shadows) trapped in the stone
Sheet / Foil - no visible scales, although fractures and lines may be present
Moonglow - luminescent glow, 1-2 colors, usually no fractures or other lines
Paintbrush - broad strokes of color
Lava Lamp - globules of color
Feather - includes small tendrils resembling feathers
Desert - the look of dry, parched land, with black lines a major feature.
Pin Fire - small scales emit sparks of light as the stone is turned
Flash Fire - larger scales emit vivid flashes of light as the stone is turned
There are 2 other "patterns" commonly referred to. I am putting these two separate, as I think they are more of a color variation of the above patterns.
Floral / Flower Garden - Bright red splotches, usually against a green background, resembling poppies in a field.
Stained Glass - there are some stones that just don’t fit into any of the above patterns, and that are best described as stained glass. There are others that still fit into one of the above categories, but the quality of the color and light in the stone is the same as the color and light produced by a richly colored leaded glass window. It is something that can’t really be described, but once seen, is unforgettable.
Stone Types
Natural - Doublet - Triplet - Mosaic - Faceted
Natural - as found in nature, more or less
Doublet - 2 pieces, put together by man
Triplet - 3 pieces, put together by man
Mosaic - a pattern created by man
Faceted - the cap - not the ammolite
Triplets often have wonderfully bright, mirror-like appearances, however I’m drawn to the depth of character found in naturals and capped naturals, and that is mostly what you will find in my jewelry. A side benefit of naturals and capped naturals being left on their original host backing is that the backing is usually much thicker and sturdier than the thin backing that is prepared for un-capped doublets and triplets. While traditional jewelry methods may have trouble with these deep stones, wire art jewelry can accommodate the depth of the stone without issue.
If everything else is equal between the stones, naturals are probably more valuable than capped naturals, which are more valuable than doublets where the ammolite has been put on a new backing, which are more valuable than triplets, which are more valuable than mosaics. However, things are rarely equal between the gem quality and pretty triplets will normally be worth more than ugly naturals.
Natural
Natural refers to a gem that has been left on its original host material and has not had any protective cap added. It may or may not be stabilized. The shale or other host material is ground down to a flat, thin backing and the ammolite is also usually ground and polished, normally to a smooth, flat surface. On rare occasions, the ammolite gem material is thick enough that the backing is completely ground away and a two-sided gem is created. Naturals are best used in jewelry that takes less of a beating, such as pendants, pins, and earrings, as well as bracelets worn only on special occasions.
Some people may argue that stabilized ammolite is an enhanced gemstone, rather than a natural gemstone. The stabilization process is done simply to prevent the ammolite from flaking/cleaving/splitting/de-laminating, like a mica. It does not alter the color, the light play, or any important aspect of the gemstone other than its stability, creating a lasting gemstone.
Doublet
Basically, doublet means 2 pieces have been bonded together to make one stone.
If the doublet has a protective cap, it is on its original matrix (ie, a capped natural). The addition of the cap helps to increase the hardness of the stone, allowing it to be used as a ring.
If the doublet does not have a cap, the gem material has been bonded to a new matrix for some reason. Unless there was a problem with the original matrix, I personally don’t understand the purpose in this - it introduces a bonded layer that doesn’t need to be there - unless they can somehow use thinner slices of the gem and make several stones from what would have been one natural.
Most of the doublets on my site are quartz-capped naturals, but I try to say specifically for each stone in the description. Protective caps are normally synthetic spinel (usually just referred to as spinel) or quartz. Some lapidaries will cap ammolite with other translucent gems, such as opal, to produce unusual effects. Protective caps increase the hardness rating of the stone and make it acceptable for use in rings and bracelets, as well as pendants, pins, and earrings. You do want to take care to protect the ammolite from sharp blows that can dislodge or break the seal of the protective cap.
Triplet
When making a triplet, a very thin layer of ammolite is attached to a backing - usually shale - which creates a doublet. A protective cap is then added. This results in 3 pieces bonded together to make one stone. Like capped naturals, triplets can be used for rings and bracelets, as well as pendants, pins, and earrings. Again, they should be protected from sharp blows.
On rare occasions, a thin layer of ammolite is made into a triplet by having a protective cap added to both sides of the ammolite. This creates a two-sided triplet with gem showing on both sides.
Different cutters give different reasons for removing ammolite from its natural matrix and reattaching it to a new backing. In some cases, there is a problem with the original backing, such as a crack. By taking very thin slices from a thick piece of ammolite, many triplets can be created from it, making a very rare gem go further. Yet another reason is to create a mosaic triplet. I believe that when Korite creates triplets, they coat the new matrix with lampblack first, to intensify the colors of the ammolite. Coating the new matrix before adhering the ammolite to it is the only color-enhancing treatment I am aware of with ammolite.
Mosaic
In general, a mosaic is a decorative design created by attaching small pieces onto a surface. To create ammolite mosaics, very thin slices of ammolite are pieced together or artfully arranged on a new backing, to create a more desirable pattern or color arrangement than was originally found in nature. Mosaics may be created strictly for an artistic purpose or as a way to use high quality pieces that are too small for any other use. All of the mosaics I have seen have had a protective cap added on top of the ammolite.
Faceted
Faceted ammolite refers to doublets or triplets with faceted protective caps. I can’t imagine wanting to put a faceted cap on a good quality stone, but the facets would probably enhance the color of a lesser quality stone.
Treatments:
Stabilization
Much (not necessarily all) ammolite is micaceous - it flakes and cleaves like mica. Because of this, ammolite is stabilized. Stabilization is an accepted treatment that has no negative impact on the gem and may enhance it slightly, by making it less directional. Stabilization is done by forcing epoxy into the layers under pressure, cementing the layers together and creating a stable stone that can be used for jewelry. Virtually all ammolite on the market has been stabilized.
Most professional lapidaries will not add any coating to the stabilized ammolite, but will just give it a final polish to show it off to its best advantage.
Polish Coating
Natural stones may have a layer of opticon, to give a higher polish to the surface.
Acrylic/Resin Coating
A clear coat is often used to protect ammonite fossils that have an outer layer of ammolite. The clear coat reflects UV rays and protects the color from fading over time and prolonged exposure to light.
Different in purpose from the above, coatings may also be used to maintain a wet look on lower quality ammolite, to improve its color.
I have also seen a layer of automotive clear coat put on a natural stone, to give it a smooth surface. (The lapidary did not want to grind that stone down to a smooth surface, as it would have taken off some of the color layers he was trying to preserve.)
These coatings are not desirable for stones to be made into jewelry, as you do not know how the coatings will hold up to the jewelry making process. Wire jewelry is probably the most suitable method for making these stones into jewelry - but if the end of a wire or tip of a pliers touches the surface, it should not cause bubbles or flakes like a coat of bad nail polish.
Blackening
When triplets (or un-capped doublets) are made, the new matrix that the ammolite is to be placed on is often made as black as possible, to intensify the colors of the ammolite. This can be done by dying the new matrix or by mixing lampblack into the epoxy.
Different effects can also be achieved by painting the matrix with a color other than black.
Care and Cleaning
Ammolite is a soft stone, like opal and composed of aragonite, like pearls. Therefore, I recommend treating them as you would an opal or a pearl.
I do put ammolite in my ionic cleaner when first made. However, for on-going care, I prefer to clean the wire with a toothbrush and toothpaste, then dip the piece into "delicate jewelry cleaner" that states on the container that it is safe for opals and/or pearls.
Do not put ammolite in an ultrasonic cleaner.
Do not leave ammolite to soak in any type of liquid.
Do not use a commercial jewelry cleaner unless it states that it is suitable for pearls and/or opals. And even then, do not let your ammolite sit in the liquid. Just dip it in and take it back out.
Take off your ammolite before applying perfumes or hairsprays.
Avoid getting various household chemicals on your ammolite.
Triplet rings with firmly affixed caps are very durable, but to be on the safe side, I would take them off when doing dishes, swimming, and other things that keep them immersed in water for a long time. I would also remove all ammolite jewelry before swimming or using hot tubs & saunas.
And, as with all wire jewelry, when you are not wearing it, I would keep it in its box, where it can not be snagged or entangled by chains and other pieces of jewelry. This is especially true if there are loose wires in the top design.
Grading and Valuing
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?
Here is a look at the topic from 4 different perspectives:
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 exists. 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 extinction.
A strong fire of one or more bright vivid colors that show from many angles.
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 angles.
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? (ie: 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? (ie: 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 flat on a table 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 is often 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 ~~ Ammonite ~~ Unearthed ~~ Misc Info ~~ Gem Stones ~~ Lore ~~ Rockhounds
This page has a variety of information regarding ammolite gem stones.
Ammolite Patterns
Stone Types
Treatments
Care and Cleaning
Grading and Valuing
Ammolite Patterns
Ammolite patterns are created by the size and shape of the scales, the presence or absence of fractures and/or black lines, and colors. Pattern names are used fairly loosely and, to some extent, pattern name can be an individual preference. But the more ammolite you see, the more patterns you recognize.
Dragonskin - small scales, reminding one of the skin on a dragon or lizard
Checkerboard - larger, blockier pattern than dragonskin
Cobblestone - like the uneven, irregular appearance of a cobblestone street
Ribbon / Banded / Striped - colors run in wide to thin bands
Wave / Ripple - water surface ripples (or their shadows) trapped in the stone
Sheet / Foil - no visible scales, although fractures and lines may be present
Moonglow - luminescent glow, 1-2 colors, usually no fractures or other lines
Paintbrush - broad strokes of color
Lava Lamp - globules of color
Feather - includes small tendrils resembling feathers
Desert - the look of dry, parched land, with black lines a major feature.
Pin Fire - small scales emit sparks of light as the stone is turned
Flash Fire - larger scales emit vivid flashes of light as the stone is turned
There are 2 other "patterns" commonly referred to. I am putting these two separate, as I think they are more of a color variation of the above patterns.
Floral / Flower Garden - Bright red splotches, usually against a green background, resembling poppies in a field.
Stained Glass - there are some stones that just don’t fit into any of the above patterns, and that are best described as stained glass. There are others that still fit into one of the above categories, but the quality of the color and light in the stone is the same as the color and light produced by a richly colored leaded glass window. It is something that can’t really be described, but once seen, is unforgettable.
Stone Types
Natural - Doublet - Triplet - Mosaic - Faceted
Natural - as found in nature, more or less
Doublet - 2 pieces, put together by man
Triplet - 3 pieces, put together by man
Mosaic - a pattern created by man
Faceted - the cap - not the ammolite
Triplets often have wonderfully bright, mirror-like appearances, however I’m drawn to the depth of character found in naturals and capped naturals, and that is mostly what you will find in my jewelry. A side benefit of naturals and capped naturals being left on their original host backing is that the backing is usually much thicker and sturdier than the thin backing that is prepared for un-capped doublets and triplets. While traditional jewelry methods may have trouble with these deep stones, wire art jewelry can accommodate the depth of the stone without issue.
If everything else is equal between the stones, naturals are probably more valuable than capped naturals, which are more valuable than doublets where the ammolite has been put on a new backing, which are more valuable than triplets, which are more valuable than mosaics. However, things are rarely equal between the gem quality and pretty triplets will normally be worth more than ugly naturals.
Natural
Natural refers to a gem that has been left on its original host material and has not had any protective cap added. It may or may not be stabilized. The shale or other host material is ground down to a flat, thin backing and the ammolite is also usually ground and polished, normally to a smooth, flat surface. On rare occasions, the ammolite gem material is thick enough that the backing is completely ground away and a two-sided gem is created. Naturals are best used in jewelry that takes less of a beating, such as pendants, pins, and earrings, as well as bracelets worn only on special occasions.
Some people may argue that stabilized ammolite is an enhanced gemstone, rather than a natural gemstone. The stabilization process is done simply to prevent the ammolite from flaking/cleaving/splitting/de-laminating, like a mica. It does not alter the color, the light play, or any important aspect of the gemstone other than its stability, creating a lasting gemstone.
Doublet
Basically, doublet means 2 pieces have been bonded together to make one stone.
If the doublet has a protective cap, it is on its original matrix (ie, a capped natural). The addition of the cap helps to increase the hardness of the stone, allowing it to be used as a ring.
If the doublet does not have a cap, the gem material has been bonded to a new matrix for some reason. Unless there was a problem with the original matrix, I personally don’t understand the purpose in this - it introduces a bonded layer that doesn’t need to be there - unless they can somehow use thinner slices of the gem and make several stones from what would have been one natural.
Most of the doublets on my site are quartz-capped naturals, but I try to say specifically for each stone in the description. Protective caps are normally synthetic spinel (usually just referred to as spinel) or quartz. Some lapidaries will cap ammolite with other translucent gems, such as opal, to produce unusual effects. Protective caps increase the hardness rating of the stone and make it acceptable for use in rings and bracelets, as well as pendants, pins, and earrings. You do want to take care to protect the ammolite from sharp blows that can dislodge or break the seal of the protective cap.
Triplet
When making a triplet, a very thin layer of ammolite is attached to a backing - usually shale - which creates a doublet. A protective cap is then added. This results in 3 pieces bonded together to make one stone. Like capped naturals, triplets can be used for rings and bracelets, as well as pendants, pins, and earrings. Again, they should be protected from sharp blows.
On rare occasions, a thin layer of ammolite is made into a triplet by having a protective cap added to both sides of the ammolite. This creates a two-sided triplet with gem showing on both sides.
Different cutters give different reasons for removing ammolite from its natural matrix and reattaching it to a new backing. In some cases, there is a problem with the original backing, such as a crack. By taking very thin slices from a thick piece of ammolite, many triplets can be created from it, making a very rare gem go further. Yet another reason is to create a mosaic triplet. I believe that when Korite creates triplets, they coat the new matrix with lampblack first, to intensify the colors of the ammolite. Coating the new matrix before adhering the ammolite to it is the only color-enhancing treatment I am aware of with ammolite.
Mosaic
In general, a mosaic is a decorative design created by attaching small pieces onto a surface. To create ammolite mosaics, very thin slices of ammolite are pieced together or artfully arranged on a new backing, to create a more desirable pattern or color arrangement than was originally found in nature. Mosaics may be created strictly for an artistic purpose or as a way to use high quality pieces that are too small for any other use. All of the mosaics I have seen have had a protective cap added on top of the ammolite.
Faceted
Faceted ammolite refers to doublets or triplets with faceted protective caps. I can’t imagine wanting to put a faceted cap on a good quality stone, but the facets would probably enhance the color of a lesser quality stone.
Treatments:
Stabilization
Much (not necessarily all) ammolite is micaceous - it flakes and cleaves like mica. Because of this, ammolite is stabilized. Stabilization is an accepted treatment that has no negative impact on the gem and may enhance it slightly, by making it less directional. Stabilization is done by forcing epoxy into the layers under pressure, cementing the layers together and creating a stable stone that can be used for jewelry. Virtually all ammolite on the market has been stabilized.
Most professional lapidaries will not add any coating to the stabilized ammolite, but will just give it a final polish to show it off to its best advantage.
Polish Coating
Natural stones may have a layer of opticon, to give a higher polish to the surface.
Acrylic/Resin Coating
A clear coat is often used to protect ammonite fossils that have an outer layer of ammolite. The clear coat reflects UV rays and protects the color from fading over time and prolonged exposure to light.
Different in purpose from the above, coatings may also be used to maintain a wet look on lower quality ammolite, to improve its color.
I have also seen a layer of automotive clear coat put on a natural stone, to give it a smooth surface. (The lapidary did not want to grind that stone down to a smooth surface, as it would have taken off some of the color layers he was trying to preserve.)
These coatings are not desirable for stones to be made into jewelry, as you do not know how the coatings will hold up to the jewelry making process. Wire jewelry is probably the most suitable method for making these stones into jewelry - but if the end of a wire or tip of a pliers touches the surface, it should not cause bubbles or flakes like a coat of bad nail polish.
Blackening
When triplets (or un-capped doublets) are made, the new matrix that the ammolite is to be placed on is often made as black as possible, to intensify the colors of the ammolite. This can be done by dying the new matrix or by mixing lampblack into the epoxy.
Different effects can also be achieved by painting the matrix with a color other than black.
Care and Cleaning
Ammolite is a soft stone, like opal and composed of aragonite, like pearls. Therefore, I recommend treating them as you would an opal or a pearl.
I do put ammolite in my ionic cleaner when first made. However, for on-going care, I prefer to clean the wire with a toothbrush and toothpaste, then dip the piece into "delicate jewelry cleaner" that states on the container that it is safe for opals and/or pearls.
Do not put ammolite in an ultrasonic cleaner.
Do not leave ammolite to soak in any type of liquid.
Do not use a commercial jewelry cleaner unless it states that it is suitable for pearls and/or opals. And even then, do not let your ammolite sit in the liquid. Just dip it in and take it back out.
Take off your ammolite before applying perfumes or hairsprays.
Avoid getting various household chemicals on your ammolite.
Triplet rings with firmly affixed caps are very durable, but to be on the safe side, I would take them off when doing dishes, swimming, and other things that keep them immersed in water for a long time. I would also remove all ammolite jewelry before swimming or using hot tubs & saunas.
And, as with all wire jewelry, when you are not wearing it, I would keep it in its box, where it can not be snagged or entangled by chains and other pieces of jewelry. This is especially true if there are loose wires in the top design.
Grading and Valuing
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?
Here is a look at the topic from 4 different perspectives:
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 exists. 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 extinction.
A strong fire of one or more bright vivid colors that show from many angles.
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 angles.
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? (ie: 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? (ie: 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 flat on a table 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 is often 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.
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