165 million year old fossilized and iridescent ammonite in superb condition.
Iridescent ammonite fossils are ancient, extinct cephalopod shells (400–65 million years old) featuring a dazzling, rainbow-like shimmer caused by fossilized nacre (mother-of-pearl) transformed into aragonite. Often found in Madagascar or Alberta, Canada, these Cretaceous-era specimens, sometimes called
Ammolite
when gem-grade, exhibit brilliant blues, greens, and reds, making them highly prized for collections and jewelry.
Ammonites are extinct, squid-like marine cephalopods with coiled, chambered shells that thrived from 240 to 65 million years ago. Known as excellent index fossils for dating rock layers, they are found globally, often exhibiting intricate, ribbed spiral patterns
. These predators related to modern coleoids lived in oceans worldwide and left behind diverse, frequently pearly fossils.
Key Facts About Ammonite Fossils
Appearance & Structure: Ammonites are characterized by a planispiral (coiled in one plane) shell, similar to the modern nautilus. Their shells were divided into chambers used for buoyancy.
- Identification Features:Paleontologists identify species using the shell's shape, ornamentation (ribs, spines, tubercles), and complex internal suture lines.
- Size Variation: While many are small, some reached massive sizes, such as the 1.4-meter (5-foot) Titanites.
- "Snakestones": Historically, coiled ammonite fossils found in Europe were called "snakestones" and were believed to be petrified snakes.
- "Buffalo Stones": The Blackfoot people of North America referred to these fossils as insikim or "buffalo stones," using them in ceremonies to call bison.
- Types of Preservation: Some fossils show incredible detail, including the original pearly nacre (mother-of-pearl) or, in rare cases, internal structures.
- Habitat: They were carnivorous, active swimmers inhabiting marine environments, ranging from the seafloor to open water.
Ammonites are popular with collectors and are often polished to reveal complex, sometimes iridescent, internal structures.