Chemical composition -- Calcium carbonate.
Color -- Dark gray with brilliant iridescent flashes of green, gold, red, and sometimes blue or purple.
Optics -- R.I 1.52-1.67.
Durability -- Hardness 4. Brittle.
Crystal structure -- Orthorhombic.
Specific Gravity -- 2.8.
Sources -- Alberta, Canada, appears to be the only known source of ammolite, a 70 million year old fossilized ammonite (a cephalopod, or squid-like animal). Ammolite is also known, less frequently, as korite or calcentine.
The iridescence occurs in the thin outer aragonite layer of the ammonite shell, which is often assembled into triplets with a protective quartz top and a shale backing.