22mm Ammolite trillion designer cabochon from Alberta, Canada

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Item Information

Dimensions (mm) 22 x 15 x 4mm
Weight (carats) 10.8 carats
Colors

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Ammolite is a rare and valuable opal-like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of the United States and Canada. It is made of the fossilized shells of ammonites, which in turn are composed primarily of aragonite, the same mineral that makes up nacreous pearls.

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.

Treatments Although fully mineralized and containing no water—and therefore not subject to dehydration and subsequent crazing—ammolite is often damaged due to environmental exposure. The thin, delicate sheets in which ammolite occurs are also problematic; for these reasons, most material is impregnated with a clear epoxy or other synthetic resin to stabilize the flake-prone ammolite prior to cutting. Although the tessellated cracking cannot be repaired, the epoxy prevents further flaking and helps protect the relatively soft surface from scratching.

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Pricing & Details

Bid Increment $1
Starting Bid $900
Auction ID 724874
Watchers 3 watching
Viewed 383 times
Starts 30th Aug 2018 12:15pm PDT
Ends 30th Aug 2018 1:09pm PDT

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