The Science of Ammolite: Formation and Colourful Iridescence Explained

Ammolite gemstones are notorious for their vibrant array of colours, ranging from deep purples to vivid greens and bold reds. In this article, we’ll explain the science behind ammolite’s colour and what gives it such brilliant properties. 

The Science of Ammolite: Formation and Colourful Iridescence Explained


Ammolite gemstones are formed from the fossilised shells of ancient marine animals called ammonites, which lived approximately 70-75 million years ago. When these animals died, their shells sank to the ocean floor and became buried under layers of sediment. 

Over time, the shells were subjected to high pressure and heat, which caused the aragonite minerals in the shells to crystallise into a new mineral called calcite. This process is known as diagenesis, and it transformed the ammonite shells into the beautiful gemstones that we know as ammolites. 

The Science of Ammolite: Formation and Colourful Iridescence Explained

Colourful Iridescence 

When light enters the ammonite shell, it interferes with multiple layers of aragonite, creating a range of colours that can shift and change depending on the viewing angle. 

The colours that we see in ammolite are primarily determined by two factors: 

  1. The thickness of the layers of aragonite 
  1. The angle of the light source 

Once harvested and turned into a gemstone, ammolite’s perceived colours can change depending on the angle of the viewer’s perspective, the direction of the light source, and the distance between the viewer and the gemstone. In other words, when it comes to ammolite, beauty is truly in the eye of the beholder. 

Gemstones as Unique as You 

Due to the scientific nature of how ammolite is formed, no two gemstones are alike. That’s why each piece of Kaimirra Tutan jewellery holds a story of its own, made with gemstones millions of years old and astonishingly unique.  

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