Red coral, scientifically known as Corallium rubrum, is a species of precious coral. Unlike the branching structures of tropical reef-building corals, this organism grows in small, leafless, shrub-like colonies deep beneath the ocean surface. The dense, mineralized material is created over centuries of slow growth. Its distinctive appearance and relative rarity have made it a coveted material since ancient times.
The Distinctive Physical Appearance
The appearance of red coral in its finished, polished form is characterized by a striking color range. The color spectrum ranges from pale salmon pink, often called “Angelskin,” to a deep, intense ox-blood red, with vermillion and orange-red hues in between. The most sought-after colors are the deepest reds, due to their rarity and saturation.
When first harvested, the skeletal material has a naturally dull, matte finish, but it is capable of taking a brilliant, glass-like polish that enhances its rich color. The material is opaque and dense, feeling heavier than expected for its size. While the color is generally uniform throughout a piece, the surface of genuine coral may show subtle natural imperfections, such as tiny pits or striations, reflecting its organic origin.
The Biological Reality of Red Coral
Red coral is not a rock or mineral, but the calcium carbonate skeleton secreted by a colony of tiny marine animals called polyps. This skeletal structure, which forms the core of the coral colony, is primarily composed of high-magnesium calcite. The characteristic red, pink, or orange coloration is not mineral-based, but comes from carotenoid pigments incorporated as the skeleton is formed.
The organism is an octocoral, which means each polyp has eight tentacles. These polyps are embedded in a soft, bright red tissue that covers the hard, tree-like axial skeleton. The valuable skeleton grows at an extremely slow rate, sometimes only one centimeter in height every few years, which is why large, high-quality specimens are particularly prized.
Where Red Coral Thrives
The species Corallium rubrum is endemic to the Mediterranean Sea and the adjacent Eastern Atlantic Ocean. It is a deep-water species, typically found in dark, low-light environments, such as marine caves, crevices, and on rocky bottoms. This coral is not dependent on sunlight for growth, unlike shallow-water reef builders, and prefers shade.
Its habitat extends over a significant depth range, from about 10 meters in shaded caves down to as deep as 300 meters. Commercially significant beds are found off the coasts of Italy, particularly Sardinia, and along the coast of North Africa, from Morocco to Tunisia. Other types of precious red coral, such as “Oxblood” or Corallium japonicum, are harvested from the deeper waters of the Pacific, near Japan and Taiwan.
Identifying Genuine Red Coral
Identifying genuine red coral involves examining several physical characteristics to distinguish it from imitations. A primary indicator is density; authentic coral feels substantial and heavy for its size, with a specific gravity typically between 2.6 and 2.7. Imitations often feel unnaturally light or, in the case of glass, too heavy and cold.
Under magnification, genuine coral exhibits a fine, wood-like grain or subtle natural striations. Fake materials tend to appear perfectly smooth or may show mold lines and excessive uniformity. A simple test for dye involves gently rubbing a hidden area with a cotton swab dipped in acetone; if the color transfers, the material has been artificially dyed, which is a common treatment for lower-quality or imitation coral.