Red Coral

 

The oldest known findings of red coral date from the Me sopotamian civilization, i.e. from about 3000 BC. For cer turies, this was the coral par excellence, and at the time c Pliny the Elder it was apparently much appreciated in India even more than in Europe. The name is derived from th• Latin corallium, related to the Greek korallion.


Appearance The red coral from the Mediterranea(Corallium rubrum) has very faint concentric rings. It is easier to see the longitudinal structures. The type from thseas near Japan has more clearly visible organic struc tures. The thin branches were and still are polishec pierced, and threaded, unaltered, into necklaces. Large pieces are cut into spherical or faceted necklace beads pear shapes for pendant jewelry, or cabochons. This cora is very compact and easily acquires a good polish, a, though this may deteriorate in time as the material is nc* very durable. It is also used for carved pieces and small ficurines, in both oriental and western art styles.


The most highly prized varieties of coral are those that arF a uniform, strong, bright red. Specimens that are too lighor too dark, or have an orange tinge or unevenly distribw color, are less valuable. Some basically red Japane corals have a white axial portion. This is, of course, garded as a defect, where it is not eliminated in the cutt process.


Distinctive features Two basic facts must be reme bered in distinguishing coral from its imitations:
1) The specimen should have the organic structure ch - acterlstic of coral;
2) On contact with a drop of hydrochloric acid (the reac available muriatic acid), the piece should display the strceffervescence characteristic of calcite.
The most frequent imitations are of glass. These have Ic gitudinal striations similar to those of coral, but do not rea: to hydrochloric acid. Another common simulant is ma, from a compact, artificial agglomerate mainly of calciwhich lacks any trace of organic structure. As mentione the hardness is about 3.5, therefore well below that glass. The organic substance in coral also gives it vFgood tenacity, far superior to that of the constituent miner alone. Because of its organic content, the density var - quite widely, but is usually about 2.60-2.66 g/cm3.

Occurrence Red coral is gathered in the Mediterrane.., (mainly near Sardinia and Sicily), the Eastern Mediterra ean, the Red Sea, and the seas around Japan.


Value When made into polished and/or faceted neclace beads, it has roughly the same value as that of certa prized ornamental stones, such as good quality turquoi~ and lapis lazuli, The color, homogeneity of each pie (individually and as part of a necklace) and polish are ve important. When the coral is made into carved pieces ar figurines, the quality of the work is obviously very impc tant. Furthermore, it should be remembered that larc pieces are hard to find.


Simulants and synthetics Very small pieces of coral - branching twigs are imitated by special glass which sim lates the typical longitudinal structures; but clearly fuse surfaces, the presence of air bubbles, and immunity to atack from hydrochloric acid uncover these imitations qui•easily, especially if they are viewed through a lens or bit ocular microscope. Nowadays, a coral-colored agglome, ate consisting mainly of calcite and called synthetic coral - also manufactured. This reacts to hydrochloric acid in th same way as true coral but lacks the characteristic struc tures of the organic version. As with other gems and ornr:mental materials of organic origin, the term synthetic is nc very meaningful.

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