ammolite, Canada, gems

Gübelin introduces ammolite as a newly recognized fossil gem material derived from the iridescent aragonitic shell layers of ammonites from southern Alberta, Canada. He discusses its fossil origin, striking opal-like play of spectral colors, structure and gemological characteristics, and its preparation and use as an ornamental stone. The material’s color results from interference within the thin aragonite layers of the preserved shell, while its relative softness and thin gem-quality layer present difficulties in cutting and jewelry use. The article represents one of the earliest gemological descriptions of ammolite as a distinct commercial gem material.