Ammolite is a unique organic gemstone, prized for its intense, rainbow-like iridescence. This rarity and beauty make it a frequent target for imitation, leading to a market filled with composite pieces and outright fakes. Understanding the science behind genuine ammolite and its construction is the most effective way to protect yourself from deceptive purchases. This guide provides practical steps to distinguish authentic ammolite from common simulants and assemblies.
How Genuine Ammolite Is Formed
Genuine ammolite originates from the fossilized shells of ancient marine creatures called ammonites, specifically the Placenticeras species, which lived approximately 71 million years ago. These shells, composed primarily of the mineral aragonite (the same substance found in mother-of-pearl), sank to the bottom of the Western Interior Seaway in what is now Alberta, Canada. The unique geological conditions in the Bearpaw Formation, including mineral-rich waters and subsequent pressure, prevented the aragonite from transforming into the more common mineral, calcite.
The aragonite layer that forms the gemstone is incredibly thin, typically less than one millimeter thick. Its dazzling color display is due to thin-film interference, where light interacts with microscopic, stacked platelets within the aragonite structure. Thicker layers of aragonite produce warmer hues (red and orange), while thinner layers yield the rarer, cooler colors (blue and violet). The natural ammolite layer is often found attached to its original host rock, usually a dark gray or brown shale.
Types of Ammolite Imitations
The majority of ammolite sold commercially is not a solid piece of the gem material but rather an assembly constructed for durability. Since the natural aragonite layer is soft (3.5 to 4.5 on the Mohs scale), it must be stabilized. This leads to the most common forms: doublets and triplets. A doublet consists of the thin ammolite layer mounted onto a solid backing, which can be the natural shale or a material like black onyx or glass.
A triplet is the most common construction for jewelry, adding a clear, protective cap over the ammolite layer, sandwiching it between the backing and the top layer. This cap is often made of synthetic spinel or quartz, which significantly increases the overall hardness of the piece. While these are not technically “fakes” if disclosed, deceptive sellers may present them as solid gemstones.
Outright simulants are made from materials with no ammolite content at all, designed only to mimic the look. These often include polymer clay mixed with iridescent powders or metallic foil flakes, then coated with an epoxy resin to achieve a glossy finish. Other low-quality fakes are created by coating sheets of plastic or glass with iridescent films or dyes. Pieces made from crushed ammolite fragments mixed with a binding agent, known as reconstituted ammolite, also exist, offering a compromised and less vibrant version of the genuine material.
Visual Cues for Detecting Fakes
The most effective way to identify a fake or composite piece is through close visual inspection of its structure and color play, ideally with ten-power magnification. Genuine ammolite displays a dramatic change in color, or iridescence, as the viewing angle shifts. A simple coated fake will often show a flat, unchanging color or only a mild, uniform sheen. The authentic material is characterized by a “dragon skin” or “cobblestone” pattern, where natural fractures in the aragonite layer create distinct, segmented patches of color.
When examining doublets and triplets, look closely at the edges where the materials meet. A clear, straight seam visible around the circumference of the stone where the top layer meets the backing is a definitive sign of a composite assembly. The presence of tiny air bubbles trapped directly beneath the clear top cap indicates a poor-quality triplet, as these bubbles are remnants of the adhesive or epoxy used in the construction.
Inspect the surface of the clear cap for signs of plastic or soft resin, which can be indicated by excessive, fine scratches or a surface that feels unnaturally warm to the touch compared to glass or natural stone. The color pattern of a simulant made from polymer clay or foil will often appear too uniform or unnaturally perfect, lacking the organic, fractured appearance of the natural fossil. If the colors are extremely vivid but do not change their hue or intensity when the stone is rotated, it suggests that a colored dye or film is responsible for the effect, rather than the structural light interference of true ammolite.