In 1981, ammolite was given official gemstone status by the World Jewellery Confederation, the same year commercial mining of ammolite began. In 2004 it was designated the official gemstone of the Province of Alberta.
The chemical composition of ammolite is variable, and aside from aragonite may include calcite, silica, pyrite, or other minerals. The shell itself may contain a number of trace elements, including: aluminium; barium; chromium; copper; iron; magnesium; manganese; strontium; titanium; and vanadium.
An iridescent opal-like play of color is shown in fine specimens, mostly in shades of green and red; all the spectral colors are possible, however. The iridescence is due to the microstructure of the aragonite: unlike most other gems, whose colors come from light absorption, the iridescent color of ammolite comes from interference with the light that rebounds from stacked layers of thin platelets that make up the aragonite. The thicker the layers, the more reds and greens are produced; the thinner the layers, the more blues and violets predominate. Reds and greens are the most commonly seen colors, owing to the greater fragility of the finer layers responsible for the blues. When freshly quarried, these colors are not especially dramatic; the material requires polishing and possibly other treatments in order to reveal the colors' full potential.
