fossil

Ammonite Fossil (Iridiscent)

Ammonoidea (subclass)

Hardness: 3.5-4.5 (Mohs), Color: Brown, tan, and cream with iridescent red/green flash, Luster: Pearly to Vitreous, Crystal structure: Orthorhombic (Aragonite based), Specific gravity: 2.6-2.85

Hardness: 3

Identified July 10, 2026More fossil →

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Physical properties

Hardness: 3.5-4.5 (Mohs), Color: Brown, tan, and cream with iridescent red/green flash, Luster: Pearly to Vitreous, Crystal structure: Orthorhombic (Aragonite based), Specific gravity: 2.6-2.85

Formation & geological history

Formed through permineralization of extinct marine mollusk shells. This specimen likely dates to the Jurassic or Cretaceous periods (66-200 million years ago) and was fossilized in marine sediment.

Uses & applications

Primarily used for jewelry (Ammolite), metaphysical healing, educational specimens, and private fossil collections.

Geological facts

Ammonites are extinct cephalopods related to the modern nautilus. The rainbow iridescence is caused by light interference within the layers of aragonite in the shell, a material often referred to as Ammolite when gem-quality.

Field identification & locations

Identify by the spiral coiled shell and visible suture patterns (frilled lines). Commonly found in sedimentary rock formations such as the Bearpaw Formation in Canada or in Madagascar and Morocco.