Study Reveals Nacre Structure Behind Ammolite Gemstone's Vivid Colors

Ammolite is a rare and vibrant gemstone derived from fossilized ammonite shells, known for its striking red, green, and blue colors linked to its nacreous (mother-of-pearl) layer composed of aragonite plates and organic materials. Recent research by Hiroaki Imai and colleagues used electron microscopy and computational simulations on specimens from Alberta, Canada, and Madagascar, as well as abalone and nautilus shells, to experimentally reveal that the brightness and vividness of ammolite's colors result from light reflecting off uniformly thin, approximately four-nanometer-wide gaps between evenly stacked aragonite plates. The study found that paler nacre colors in other samples result from larger or absent gaps, more organic material in the gaps, or uneven layer distribution. These nanoscale structural differences make ammolite's coloration particularly intense and non-fading, a feature that could inspire the development of durable colored paints. The findings clarify the physical origins of ammolite's unique coloration, confirming theories of light interference and reflection at the nanoscale. This research advances understanding of gemstone coloration and highlights ammolite's exceptional nature among fossilized shells.