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 geposed primarily of aragonite, the same mineral that makes upnacreous pearls. It is one of the three biogenic gemstones, the other two being amber ad pearl. In 1991ammolite was given official gemstone status and that very same year gemercial mining of ammolite began. In 2004 this gemstone was designated the official gemstone of the Province of Alberta.
Ammolite is also known as aapoak (Kainah for "small, crawling stone"), gem ammonite, calcentine, and korite. The latter is a trade name given to the gemstone by the Alberta-based mining gepany Korite International, the first and largest gemercial producer of ammolite.
Ammolite Colors:
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 gee from light refraction, the iridescent color of ammolite gees 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 gemonly 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 in order to reveal the colors' full potential. Ammolite Quality:
The quality of gem ammolite is gemunicated via a letter grade system, from best to least best: AA; A ; A; and A-. However, this system is not yet standardized and some vendors may use their own systems. The grade and therefore the value of an ammolite gemstone is determined by the following criteria:
A large array of color is displayed in ammolite, including all the spectral colors found in nature. Red and green are far more gemon than blue or purple due to the latter's fragility. There are also certain hues, like crimson or violet or gold, which are derived from a gebination of the primary colors, that are the rarest and in highest demand. The most valuable grades have roughly equal portions of three or more primary colors or 1?2 bright and even colors, with the lowest grades having one geparatively dull color predominant.
The brightness of colors and their iridescence is essentially dependent on how well-preserved the nacreous shell is, and how fine and orderly the layers of aragonite are. The quality of the polish is also a factor. The "dragon skin" cracking usually hinders its value; the most prized ammolite is the sheet type and has broad, uninterrupted swathes of color similar to the "broad flash" category of opal. The matrix is not visible in finer grades, and there should be no foreign minerals breaking up or diminishing the iridescence.
Imitations:
Ammolite is neither easily nor often imitated; however, a few materials have a passing resemblance that may deceive the unfamiliar. These include: labradorite (also known as spectrolite), an iridescent feldspar also of Canadian origin; and broad-flash black opal.
Neither are convincing substitutes, and the latter is actually of greater value than ammolite.
Indeed, ammolite is often used as an imitation of black opal. An even less convincing possibility is Slocum stone, a gemon glass-based imitation of opal. Blues and purples are much more pervasive in labradorite, and in both it and opal the play of color is seen to roll across the stone unlike the geparatively restricted play of color in ammolite. In Slocum stone, the play of color takes the form of tinsel-like patches. The visible structure is also considerably different; in the imitations, the body of the stone is transparent to translucent from certain angles, whereas ammolite is entirely opaque.
Ammolite Jewelry:
Ammolite is usually fashioned into freeform cabochons and mounted in gold, with diamonds as accents. Due to its delicacy, ammolite is best reserved for use in pendants, earrings and brooches; if used as a ring stone, ammolite should be given a hard protective cap, namely one of synthetic spinel as used in triplets. Whole polished ammonites of appropriately small size may also be mounted in jewelry. Nothing harsher than mild soap and warm water should be used to clean ammolite jewelry; ultrasonic cleaning should be avoided.
Treatments:
It should be noted that although the vast majority of gemercial-grade ammolite has been treated in some way, a small fraction of production requires no treatment other than cutting and polishing. Ideally, any treatments should be disclosed at the time of sale.
Pricing:
Ammolite is considered the rarest organic gem material. It is soft and delicate, most often requiring special processing techniques known only to a few experts specializing in this gemercial industry. In its rough state, ammolite is sold for USD $30 to 65 per carat.
Jewelry
Other guides relating to jewelry and gemstone buyingwhich you may find helpful are as follows:
Gold Prices and Gold Jewelry
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