Most commercial mining operations have been conducted along the banks of the St. The best grade of gem quality ammolite is along high energy river systems on the eastern slopes of the Rockies in southern Alberta. However, small deposits have been found as far south as Central Utah which also contains gem-quality ammolite.
Significant deposits of gem-quality ammolite are only found in the Bearpaw Formation that extends from Alberta to Saskatchewan in Canada and south to Montana in the USA. K Korite's mechanized mining operations are fairly basic, involving the excavation of shallow pits with backhoes. Most fossilized shells have had their aragonite pseudomorphously replaced by calcite or pyrite, making the presence of ammolite particularly uncommon. While these shells may be as large as 90 centimeters (35.5 inches) in diameter, the iridescent ammonites (as opposed to the pyritized variety) are typically much smaller. Occasionally a complete ammonite shell is recovered with its structure well-preserved: fine, convoluted lines delineate the shell chambers, and the overall shape is suggestive of a nautilus. Ammolite mined from deeper deposits may be entirely smooth or with a rippled surface. The cracking results in a tessellated appearance, sometimes described as a " dragon skin" or " stained glass window" pattern.
#Korite ammonite crack#
So-called "frost shattering" is common exposed to the elements and compressed by sediments, the thin ammolite tends to crack and flake prolonged exposure to sunlight can also lead to bleaching. Rarely is ammolite without its matrix, which is typically a grey to brown shale, chalky clay, or limestone. The ammolite itself is actually a very thin sheet, ca.
#Korite ammonite full#
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. Reds and greens are the most commonly seen colors, owing to the greater fragility of the finer layers responsible for the blues. The thicker the layers, the more reds and greens are produced the thinner the layers, the more blues and violets predominate. 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. Under ultraviolet light, ammolite may fluoresce a mustard yellow.Īn 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 refractive index of Canadian material (as measured via sodium light, 589.3 nm) is as follows: α 1.522 β 1.672–1.673 γ 1.676–1.679 biaxial negative. Its hardness is 4.5–5.5, and its specific gravity is 2.60–2.85. The shell itself may contain a number of trace elements, including: aluminium barium chromium copper iron magnesium manganese strontium titanium and vanadium.
The chemical composition of ammolite is variable, and aside from aragonite may include calcite, silica, pyrite, or other minerals. The latter is a trade name given to the gemstone by the Alberta-based mining company Korite, the first and largest commercial producer of ammolite. Īmmolite is also known as aapoak ( Kainah for "small, crawling stone"), gem ammonite, calcentine, and Korite. It was designated the official gemstone of the City of Lethbridge, Alberta in 2007. 1 In 1981, ammolite was given official gemstone status by the World Jewellery Confederation (CIBJO), the same year commercial mining of ammolite began. It is one of few biogenic gemstones others include amber and pearl. It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral contained in nacre, with a microstructure inherited from the shell. Usually 1.52 - 1.68 (varies with mineral content) Īmmolite is an opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of North America.
Usually about 2.70 (varies with mineral content) Gray to brown, can be radiant blue,with primarily red to green iridescence. Unprocessed sample of ammolite, a "dragon skin" pattern is apparentĬaCO 3 aragonite polymorph, with minor amounts of calcite, pyrite, silica, and other impurities
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