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Ammolite is known as an exceptional and expensive macrobiotic gemstone of opal shape discovered mainly along the eastern slopes of the Rocky Mountains of the United States and Canada. The stone is made of the fossilized shells of ammonites; those were once a group of marine animals which are now extinct species. The ammonite is composed mainly of aragonite a carbonate mineral.
Ammolite appears gray to brown and sometimes with shimmering colors with greasy to dull Luster when polished the luster becomes vitreous. Refractive index of the stone usually lies between 1.52 - 1.68 that can vary with mineral content of the stone. The Birefringence of the stone constitutes usually 1.55 with a variable Ultraviolet fluorescence. The Specific gravity is usually about 2.70.
Ammolite as a gem stone has some superior qualities that make it a real gem. The system followed to characterize the quality of the gemstone ammolite is corresponded through a letter grade system that initiates from best and terminates to least best as AA; A+; A; and A-. The system is not yet standardized but it is mainly in use. The value of the gemstone is verified through various factors that includes
The number of primary colors
The way the colors play scientifically termed as chromatic shift and rotational range
Brightness of colors or iridescence
Ammolite is distinguished as the rarest macrobiotic gemstone. The stone is characterized as malleable and fragile and so the stone involves exceptional processing procedures that are known only to not many professionals specializing in this commercial industry. The price of an ammolite in unprocessed state is USD $30 to 65 per carat or 150 to 325 $/g.
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