Reference work entry
The term coral gem mainly refers to gem-grade red coral. Coral is a coelenterate that secretes lime (calcite) during the growth process to construct their bodies. To obtain food and sunlight, corals form dendritic groups. Its chemical composition is CaCO 3, and it is composed of microcrystalline calcite aggregates. Coral is generally white and can also be red, pink or orange red. There are also rare black and blue corals. Red coral with a translucent waxy lustre and a fine texture is considered a high-quality gem (Fig. 48).
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