What Gives Ammolite Its Colour?

One of the first things people notice about Ammolite is its extraordinary colour. Brilliant flashes of red, green, blue, purple, gold, and countless shades in between can appear to move and change as the stone is turned in the light.

Unlike many gemstones, however, these colours do not come from pigments or trace minerals within the stone. Instead, Ammolite's colours are created by the way light interacts with the fossil shell itself.

This unique optical phenomenon is what makes Ammolite one of the most visually distinctive gemstones in the world.

Colour Created by Light

Ammolite originates from the fossilized shells of ancient ammonites that lived more than 70 million years ago. These shells were composed primarily of aragonite, a mineral that forms the outer shell of many marine organisms.

Under the right conditions, portions of the shell were preserved during fossilization while retaining their original microscopic structure.

The shell consists of countless ultra-thin layers of aragonite stacked one on top of another. When light strikes these layers, it reflects back at different wavelengths. Some wavelengths are amplified while others are cancelled out, producing the brilliant iridescent colours that Ammolite is famous for.

This phenomenon is known as iridescence or play-of-colour.

Similar effects can be seen in soap bubbles, peacock feathers, butterfly wings, and opal, although Ammolite displays its own unique patterns and colour combinations.

Why Do the Colours Change?

One of the most fascinating characteristics of Ammolite is that its colours often appear to shift as the stone moves.

This occurs because the angle of the incoming light changes which wavelengths are reflected back to the viewer. A stone that appears predominantly green from one angle may reveal flashes of red, gold, blue, or purple when viewed from another.

This constantly changing display is part of what makes Ammolite so captivating both in jewelry and collector specimens.

Why Are Some Colours Rarer Than Others?

Not all Ammolite colours occur with the same frequency.

The thickness of the aragonite layers plays a major role in determining which colours are visible. Generally speaking, thicker layers tend to produce reds, oranges, and greens, while thinner layers produce blues and purples.

Because the conditions required to preserve these thinner layers are less common, blue and purple Ammolite are among the rarest colours encountered.

These colours are often found near the outer surface of the shell, where millions of years of weathering and oxidation may have destroyed them before the fossil was ever discovered. As a result, specimens displaying strong blues, purples, pinks, or multiple colours at once are especially prized by collectors.

Patterns, Not Just Colours

Colour is only part of the story.

The arrangement of the shell layers, natural fractures, growth structures, and fossilization processes can create a wide variety of patterns within Ammolite. Some stones display broad sheets of colour, while others reveal intricate mosaics, stained-glass effects, dragon skin textures, ribbon patterns, or floral-like designs.

These patterns interact with the colour display to create an almost endless variety of appearances.

No two shells fossilized under exactly the same conditions, which means no two gemstones will ever look exactly alike.

A Natural Masterpiece

Every piece of Ammolite represents a unique combination of biology, geology, and time.

The colours seen today are the result of microscopic shell structures created by a living animal more than 70 million years ago and preserved through an extraordinary fossilization process. The result is a gemstone unlike any other—one whose colours are not created by pigments, but by light itself.

This combination of rarity, colour, and individuality is what makes Ammolite one of the world's most fascinating gemstones.