How Ammolite Gems Get Their Vivid Colors

The origin of the vivid colors within the gemstone ammolite – a rare type of brightly colored fossilized ammonite shell – has been published in research. Scientific reports.

The colors of ammolite are found within a protective layer of nacre—also known as mother-of-pearl—which contains layered plates of the mineral aragonite and a small amount of organic material such as protein. Although it is believed that the colors of ammolite are produced by the interaction of light with these layers, the origin of these colors has not been experimentally evaluated.

Hiroki Amai and colleagues investigated the structural and optical properties of ammolite samples from Alberta, Canada, using electron microscopy and imaging. They then compared them to ammonite fossils from Madagascar, as well as abalone and nautilus shells, with the features of the paleer necker.

The authors identified a similar structure of stacked aragonite plates within all samples but found that the thickness of these plates and the size of the gaps between them varied.

They found that the brightness of the ammolite colors is caused by light reflecting off the four-nanometer-wide gap between the aragonite plates and also by the distribution of layers of uniform thickness within the nacre.

They suggest that the paler color of the nacre in other samples is due to large gaps or lack of spaces between the aragonite plates, the presence of organic material in these spaces, or variations in the distribution of layers within the nacre.

The authors suggest that their findings could inform the development of non-fading paints.