Red Coral

Hardness: 3-4 (Mohs), relatively soft. Color: Red (from pale pink to deep oxblood), often with veining or lighter patches. Luster: Vitreous to waxy when polished. Crystal Structure: Not crystalline; it has a non-crystalline, porous, and fibrous internal structure composed of aragonite microcrystals. Cleavage: None. Specific Gravity: 2.6-2.7.

Formed by tiny marine animals (polyps) that grow in colonies in tropical and subtropical waters, at depths ranging from a few meters to over a thousand meters. They secrete a hard, calcareous exoskeleton (composed primarily of calcium carbonate in the aragonite form) to create the coral reef structure or individual coral branches. The red color in precious coral is due to carotenoid pigments. Its formation takes thousands of years, with growth rates being very slow (e.g., Corallium rubrum grows only a few millimeters per year). Geologically, coral reefs have existed for millions of years, but the individual coral skeletons used for jewelry are relatively modern.

Primarily used as a gemstone in jewelry (beads, cabochons, carvings) and for decorative objects. Historically, it was also used for medicinal purposes in various traditional cultures, although this is not scientifically supported. Due to its endangered status, sustainable alternatives and antique pieces are increasingly sought after.

Coral has been used for adornment since ancient times, with archaeological finds dating back to the Stone Age. Red coral, specifically Corallium rubrum, is highly prized due to its intense color and has been culturally significant in many civilizations, often associated with protection and good fortune. Despite its popularity, red coral is now endangered due to overharvesting and environmental factors, leading to strict regulations and CITES listings to protect its remaining populations. Plastic and dyed bone or shell are common imitations.

In the field, natural red coral grows underwater in colonies, often forming elaborate treelike or fan-like structures attached to rocky seafloors. Identification of the finished product (beads as seen in the image) in the field involves examining its color, texture, and other properties. Tips for collectors: Genuine coral will have a slightly porous texture, sometimes with small pits or growth lines. It feels cool to the touch and has a distinct waxy luster when polished. Be wary of plastic imitations (which often feel warmer and lighter) or dyed materials (which may show uneven coloring or dye concentration in crevices). The beads in the image appear to be classic red coral beads, often used in tasbih (prayer beads) or other jewelry. Common locations for natural red coral harvesting include the Mediterranean Sea, the Pacific Ocean (especially near Japan and Taiwan), and the Red Sea, though much of this activity is now highly regulated or prohibited.