Precious coral could be a stone quality type of natural coral, closely associated with reef-building 'stony' coral. Precious coral could be a problem coral that forms in rocky seabeds with low levels of deposit, usually in dark environments of over 500 feet deep, together with caverns and crevices.
Precious coral is slowly designed by awfully small aquatic animals referred to as coral polyps. These tiny, soft-bodied creatures kind with minute, onerous shells that accumulate because the colony grows. Over time, the colony begins to generate higher branches and very lanky structures invented of hardened carbonate and colored by antioxidant pigments.
Precious coral gemstone usually exhibits a spread of heat chromatic to red colors, as well as light-red to salmon (momo coral), and medium-red (Sardegna coral) to deep ox-blood red (moro coral); color is known to fade when damaged. Noble coral has the prime attractive uniform color, however, it will usually exhibit streaks or spots of white to chromatic red. Precious coral gemstone can also be found in other colors such as gold, white, black and blue.
Gold colored coral from Hawaii is extraordinarily rare & extremely desired for its slight chatoyancy. Black and blue coral are not often used for gems or jewelry as its trade is heavily regulated.
Coral Clarity and Luster
Precious coral is usually transparent to opaque. When unworked, it has a naturally diffuse, dull luster. Polished coral exhibits an attractive vitreous luster. Coral is polished with fine-grain sandstone and emery, and then finely polished with felt-wheels.
Coral Cut and Shape
Precious coral is most often cut en cabochon due to its softness and opacity. It is popularly used for beads, ornamental carvings, and sculptures. Cabochons can be found in just about any figure, but ovals, rounds, and free-form shapes are most popular.
Natural coral is usually raw, but some materials may be dyed to achieve a more valuable color. There are a variety of other materials used to imitate coral, such as glass, bone, conch shell and plastic.