The pearl is round the body, which are formed in the shells of some mollusks in the encapsulating particles that fall into them, with the aim of protecting the body of the mollusk from irritation of these particles. Enveloping substance forms the mantle of the mollusk, which is a fold of his body. This substance is a mother of pearl . Perlmutter - "mother of pearl"). It consists of two components : inorganic and organic. The inorganic component is calcium carbonate, simply put, is chalk. The form in which the calcium carbonate in mother of pearl and pearls, called aragonite. Organic component is a Horny substance consisting of protein (conchiolin). Pearl consists of several thousand very thin concentric layers of aragonite in the form of hexagonal plates, separated by the "leaves" of conchiolin. On average, pearls contain approximately 86% of calcium carbonate, 12% organic matter and 2% water.
The structure of pearls
The formation of a pearl starts from the center with the deposition of layers of aragonite, consisting of prismatic crystals. While out of organic matter, which is concentrated at the base of the crystals and between growing aragonite prisms. After some time, the growth of aragonite prisms suspended, however, organic matter continues to stand out and to fill the gaps between the crystals of aragonite. Soon the deposition of organic matter stops and starts again the formation of prismatic crystals of aragonite on the same organic basis. The process rhythmically repeated, gradually form new layers of aragonite with layers of organic matter.
Outside of the prismatic layers grow lamellar layers of aragonite, causing pearly luster of pearls. The thickness of the pearl shell pearl is about 0.5 mm
Since pearls are composed mostly of calcium carbonate, it is easily soluble in acids, even in a weak (e.g., acetic acid). However, weak acid dissolution is much slower than the strong. For example, in hydrochloric acid pearl dissolves within a few seconds, and acetic acid it will dissolve a few days.
When heated pearls decomposes.
Typical pearly luster of the pearl is the result of interference of light in thin wavy discs of mother of pearl.
The color of a pearl depends on the type of the host mollusk. He is influenced by impurities in the water, in which lives the shell-oyster. So the color of pearls depends on the geographical habitat of shells that produce it. So, the pearls are harvested off the coast of Japan and India, has a high gloss and a pinkish hue, Australian white, Panamanian Golden, Caribbean - red-brown. That is why the experts can color pearls to assume a place where it was produced.
In addition, the coloring of pearls is affected by temperature and composition of the water, the health of the clam and the nature of food, which it digests.
Color of pearls depends on many factors
Interestingly, the pearls are rare pure white. Usually it is silver in colour, sometimes cream or pink. There are also yellow, green and even black pearls.
The rarest and most expensive pearls are greenish - blue, they are found only off the coast of Indonesia.
Size secrete pearls are tiny; small (up to 2.5 mm); medium (2.5-6 mm) and large (over 6 mm). Pearls with a diameter of more than 7-8 mm - high quality jewelry. They are rare and are incredibly high. The size of the large pearls can be from 10 to 15 millimeters. The London Museum pearl weighing 85 grams, its diameter is 45 mm.
Conchiolin in the composition of the pearls are prone to desiccation, and for this reason the pearls without proper care can live only 50-150 years and then "dies": first, he dims ("sick"), then it appears the cracks and begins peeling the shells. This is why pearls absolutely contraindicated dry and too humid air, and exposure to fats, acids, perfumes, human sweat. As these impacts are unavoidable when using pearls as jewelry, experts advise to remember the rules of care: keep away from sunlight; keep it wrapped in a soft cloth and from time to time dipped in a container of water for several hours, then dried in a cool place.
With proper care and in the absence of contact with air, pearls can be stored indefinitely. Known gems that 400-500 years, for example the pearls from the Treasury of the British Royal house. And in Japan even found a burial with pearls older than 1000 years!