There’s an organic gemstone you’ve probably heard of—though you may not be entirely familiar with it: opalite. As one of the organic biogenic gemstones (which also include pearls, amber, and coral), opalite is a fossilized shell of a nautilus that dates back 70 million years. It wasn’t until the past 50 years that it was recognized as an important gemstone.

As for banded agate, you could say it’s incredibly ancient—after all, it thrived on Earth at the same time as the dinosaurs and then mysteriously vanished alongside them. Yet you could also describe it as remarkably young, since it wasn’t officially recognized by the World Jewellery Confederation as a new gemstone until 1990, marking the beginning of its true commercial mining and sales—and adding yet another, youngest member to the family of colored gemstones.

The name "Ammonite" derives from Amun, the ancient Egyptian sun god—supposedly because its shape closely resembles the spiraling ram’s horns atop this deity’s head. Although nautilus fossils can be found all over the world, the most distinctive and brilliantly dazzling specimens are those of gem-quality ammonites mined in southern Canada.

75 to 70 million years ago, the area where opalized nautiluses are found was once a warm, shallow sea teeming with a diverse array of nautiluses. Frequent orogenic movements in the Rocky Mountains triggered frequent volcanic eruptions, which deposited layers of volcanic ash several meters thick onto the sea surface. As a result, countless marine organisms living in the shallow sea died rapidly and were buried beneath these layers. Over time, the volcanic ash accumulated to a thickness of four kilometers in this region. Later, as a result of subsequent crustal movements, the strata of the former shallow sea gradually rose closer to the Earth's surface. The nautiluses that had been buried deep beneath these layers, thanks to the abundant iron and magnesium elements and the protective seal provided by the volcanic ash, eventually evolved into the world’s unique fossilized nautilus—opalized nautiluses.

Despite enduring the vicissitudes of time, the region’s uniquely favorable geological conditions have perfectly preserved the distinctive characteristics of opal, transforming it into genuine opal gemstones of gem-quality that hold commercial value.

The Bearpaw Shale Formation in southern Alberta, Canada, is the only region worldwide where high-quality opal can be mined. Several hundred years ago, local residents living along the St. Mary River stumbled upon some colorful stones embedded in the rock layers. When exposed to sunlight, these stones emit a dazzling spectrum of colors; and if you rotate the stone, its hues seem to shift and change—truly remarkable. At the time, people believed that these stones had absorbed the essence of heaven and earth and possessed magical powers, so they began wearing them as "amulets." It’s no wonder, then, that opal later became Canada’s national gemstone—after all, traces of its iridescent beauty can be found nowhere else on Earth except for a narrow, elongated strip of land in southern Canada.

Each piece of opal contains numerous layers—think of it as a book bound together by many pages. When sunlight shines on these different layers, “diffraction” occurs (a physical phenomenon in which light waves bend away from their original straight path when encountering an obstacle), producing a variety of colors. Since the number of layers varies in each opal and the pressure exerted by the overlying rock layers during its formation underground is also uneven, the surface cracks take on unique characteristics. As a result, every opal boasts distinct colors, textures, patterns, and surfaces, making each one utterly unique.

Banded ammonites differ significantly from ammonite fossils found in other parts of the world, which typically exhibit only slight iridescence and predominantly dull colors—often shades of brown. As a result, their prices can differ by as much as a hundredfold. Please be careful to distinguish between them. For example, another type of small ammonite fossil found in Madagascar may display subtle, localized iridescence against a yellow background. Many traders will claim that such fossils are banded ammonites, but in reality, fossils at this level are still far from being true banded ammonites. Not only are they far more abundant, but they also differ dramatically in terms of aesthetic appeal and intrinsic value.

Diaspore comes in three main types: purely natural, coated, and laminated. Prices range from high to low accordingly. Fragile specimens require protection with a crystal coating to prevent damage. Typically, small, regularly shaped diaspore particles that are used for inlay have undergone coating treatment. Purely natural diaspore—a rarity on the market—is usually found in irregular, large chunks and commands a hefty price.

Moreover, today’s ore-mining methods resemble those used in open-pit coal mining: people use excavators to directly strip away the overlying rock layers. This practice causes significant damage to the local ecological environment. As a result, ore mining is strictly regulated in the area, meaning that the actual amount of opalite mined is extremely limited—and complete fossil specimens are even rarer.

Experts estimate that, at the current rate of extraction, Canada’s opal mines will be depleted in roughly 20 years. If no new deposits are discovered in the future, opal will “face extinction once again.”