How to distinguish coral from fake?
What are corals and what types of jewelers use
Corals are not stones, but the external skeleton of an invertebrate predatory animal, roughly speaking, the “bones” of many polyps. The size of a single marine organism in a colony is only 1-2 mm. In the process of life, a polyp, feeding on plankton, forms calcium and magnesium carbonate, an oxide of iron, from the components of seawater, thus forming an exoskeleton. The organic component in 1% gives color shades of corallite. The depth also affects the color.
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Coralite of the same species, but grown in different conditions, differs in shape and color.Coral trees grow slowly: in width - a few millimeters per year, and in a length of 1-7 cm. Overgrown coral reefs still slow down their growth and eventually collapse. Coral polyps can live in any ecologically clean seas at temperatures up to +4 ° C, but reefs can be built only where algae survive, providing a colony with nutrients, that is, at t not less than +18 ° C.
Types of natural coral
Coral raw materials for jewelers at the place of production is divided into Mediterranean and Pacific. The following types of natural corals are distinguished:
- Approximately 25 types of coral polyps are formed.from calcite and aragonite(polymorphic modification of calcium carbonate). Jewelers call them "noble." These are mainly gorgonian - horn corals of the Corallium rubrum species with different colors: from white to black, more than 350 colors. Each color has its own name, sometimes poetic: “angel's skin”, “bovine blood”, “greatest”, “marine bamboo”. Most often for stone-cutting work, red and pink are used. And in the old days, the dark ones were specially lightened, and now the whites are tinted to a bright color.
- There are also soft coral polyps that harden in the air, while remaining quite porous. Can fully consistfrom organic material. On the Internet, they are often called "Black Akkabar". But this is not entirely true. Because completely organic polyps, such as the fans of Ctenocella or Ellisella, which are at the stage of extinction, can be of other colors: red-pink, black, even golden, blue and amethyst.
- There is a fossilagate coral. Found deposits in the United States (Florida and Michigan), in Russia, but is not widely used.
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Coral branches are valued with greater hardness (from 3.5-4), they are called "royal". Usually these are deep-sea species. Previously, the complexity of mining and hardness prevented their use in jewelry, so they were more easily processed. At present, it is easier to extract ornamental material, but since 1963, there has been a ban on the harvesting of corals in many countries because of the IUCN (World Conservation Union) resolution.
How Corals Are Forged
Demand, slow recovery, the death of reefs due to ecology and predatory extermination, prohibitions on extraction cause a high price of natural coral products.A real red coral is an expensive rarity, one bead can cost about $ 50. Instead, at best you will be sold a painted white. At worst:
- Imitations that are quite a place to be, if so stated.
- Counterfeit. When a quality item is given a low-grade, or frank fake of minerals, glass, polymers or plastic. This is a fraud.
In jewelry, "sea trees" have been used since time immemorial, and even then there were fakes, they are found in ancient burials. In the tomb of Tutankhamen were found glass beads that mimic coral.
It is profitable to fake only colored coral species, because white is cheap. Previously, coral beads produced glass, petrified dyed bones (odontolite), porcelain, horn, and minerals: quartzite, howlite, cacholong.
With the growth of technology, how to forge corals has become more: polymer resins, plastics, the Neolithic (a compound of copper phosphate and aluminum hydroxide) have appeared.
Separately, there are "pressed" coral blanks. The crumb and powder of the shells of mollusks, as well as the mineral aragonite or calcite (calcite) are discolored by acid treatment and combined with polymer composites. Then paint over.To the marine exoskeleton of the polyp is related only that in the composition of the counterfeit there is calcinite.
Since the 70s. synthetic Gilson's coral is also made from calcite powder. (Named in honor of the owner of the Swiss company, who also invented a cheap substitute for black opals.) And recently in the Philippines, a new technology appeared to imitate a rare Hawaiian golden variety.
If a good imitation is offered at a reasonable price, especially from "long-playing" minerals, like golitis, then the purchase is quite successful. It's a shame when a fake is given for expensive coral.