Why Does Ammolite Change Colour?

One moment, Ammolite reveals flashes of deep green and gold. In another light, the same gemstone may shift to brilliant reds, blues, or violet.

This dramatic play of colour is one of Ammolite’s most captivating qualities—and one of the most scientifically fascinating.

Unlike traditional gemstones, Ammolite’s iridescence is not created by pigment or dye. Its colour comes from the preserved shell structure of ancient Canadian Ammonites, marine animals that lived more than 70 million years ago in the prehistoric seas of what is now southern Alberta, Canada.

The result is a gemstone unlike any other: one shaped by ancient marine life, geological preservation, and the interaction of light itself.

The Science Behind Ammolite’s Iridescence

Ammolite’s colour is created through a phenomenon known as thin-film interference.

The shell of the Ammonite was composed primarily of aragonite, a crystalline form of calcium carbonate also found in pearls and many modern marine shells. In rare cases, these microscopic layers survived fossilization over millions of years.

When light reaches the preserved layers of aragonite, certain wavelengths are reflected while others pass through. The thickness and structure of these layers determine which colours become visible to the eye.

This is why Ammolite can display such vivid and shifting colouration—from fiery reds and greens to flashes of blue and violet.

Unlike surface treatments or artificial coatings, these colours are entirely natural, created by the preserved structure of the shell itself.

Why Ammolite Looks Different in Every Light

One of the defining characteristics of Ammolite is that its appearance changes depending on the angle of light and the perspective of the viewer.

As light moves across the gemstone, different layers within the shell reflect different wavelengths. This creates the dynamic shifting effect known as iridescence.

No two Ammolite gemstones ever reveal colour in exactly the same way.

Some display broad flashes of colour, while others reveal intricate mosaic or stained-glass-like patterns formed naturally within the shell. This individuality is part of what makes Ammolite so compelling to collectors, jewellers, and gemstone enthusiasts alike.

Why Some Ammolite Colours Are Rarer

Not all Ammolite colours occur with the same frequency.

Red and green are among the most commonly occurring colours, while vibrant blues and violets are considered far rarer due to the thinner aragonite layers required to produce them.

Full-spectrum gemstones displaying multiple vivid colours together are exceptionally uncommon.

The intensity, range, and brightness of colour all contribute to the rarity and desirability of an Ammolite gemstone.

Did you know? Only 3–5% of mined Canadian Ammonites yield gem-quality Ammolite.

Preserved by Time and Nature

Gem-quality Ammolite occurs almost exclusively in southern Alberta, Canada, where unique geological conditions allowed the delicate shell layers of ancient Canadian Ammonites to be preserved.

Over millions of years, most Ammonite shells transformed into more stable minerals during fossilization. Ammolite exists because, in rare cases, the original aragonite structure survived.

This extraordinary preservation allows light to interact with the shell in ways that continue to captivate scientists, collectors, and jewellery lovers alike.

Discover the Colour of Ammolite

Every Ammolite gemstone carries its own natural pattern, structure, and spectrum of colour—preserved from a prehistoric ocean more than 70 million years ago.

Explore KORITE’s collection of natural Ammolite jewellery and discover one of the world’s rarest expressions of colour and light.

Continue Exploring Ammolite

Curious about the connection between Ammolite and other organic gemstones?

Explore our article:
Ammolite and Pearl: A Shared Origin Beneath the Sea

You can also learn more about the differences between Ammolite and Opal in our article:
Opal vs Ammolite: What’s the Difference?