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How Is Ammolite Graded?

How Is Ammolite Graded? thumbnail
Ammolite is a gemstone derived from a fossilized animal called an ammonite.

Ammolite is one of the world's rarest gemstones, highly prized for its opal-like iridescence and vibrant colors. There is no universally recognized system for grading ammolite, but some standards do exist.

  1. Grading Properties

    • According to Tom Dryden, a renowned expert on ammonites, almost all existing ammolite grading systems evaluate the gemstone with respect to its color and iridescence. Green and red are the most common colors of ammolite, while blue, violet and pink are rarer. The higher grades of ammolite display a wide range of vibrant colors, while the lower grades have fewer hues. Iridescence can be described as how brightly color is reflected from the surface of a gemstone. The best grades of ammolite are categorized as brilliant.

    Higher Grades of Ammolite

    • The highest grade of ammolite (AA or Exquisite) clearly presents three or more colors and is brilliantly iridescent. An A+ gemstone displays two colors with a bright iridescence. An A graded ammolite has one distinct color (usually green or red) and is less vibrant.

    Lower Grades of Ammolite

    • The A- or Standard gemstone is dark, while the B graded (Fair) stone displays muddied colors. Finally, the commercially rated ammolite (C) has neither color nor brilliance.

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  • Photo Credit ammonite image by Goran Bogicevic from Fotolia.com

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