Precious red coral is a highly sought-after material for jewelry due to its intense color and natural rarity. It is an organic gem composed of a hard skeleton secreted by marine polyps. This unique origin has made it a valuable commodity for centuries, leading to a market flooded with various imitations. Accurate identification is necessary for consumers to protect their investment and avoid supporting the trade of misidentified materials.
Physical Characteristics of Authentic Red Coral
Authentic red coral is primarily composed of calcium carbonate, which forms the dense, internal skeleton of the organism. Before being polished, this material naturally possesses a matte or waxy finish, often exhibiting a beautiful sheen after processing. The color of genuine coral ranges from pale pink to deep “ox blood” red, caused by carotenoid pigments within its structure.
This coloration is rarely perfectly uniform and often shows minor variations, subtle marbling, or slight unevenness across the surface. A perfectly monochromatic piece may suggest the material has been artificially dyed to achieve a flawless look. Genuine coral possesses a specific gravity between 2.6 and 2.7, giving it a noticeable density that makes it feel heavier than many plastic or resin imitations.
Identifying Common Imitation Materials
Counterfeit red coral is manufactured from various materials. One common imitation involves dyeing porous materials like bamboo, bone, or howlite stone. These fakes often reveal concentrated dye accumulation in small fissures, pores, or carved details upon close inspection.
Another frequent substitute is glass, sometimes referred to as Slocum Stone. Glass can be identified by its overly high, glassy luster and the presence of conchoidal (shell-like) fractures if chipped. Tiny air bubbles trapped within the material are also a definitive sign of glass visible under magnification.
Plastic and resin fakes are typically the easiest to spot because they are significantly lighter than authentic coral. These synthetic pieces often exhibit a slick, uniform surface and may even show subtle mold lines where the piece was formed.
Reconstituted coral is a more deceptive imitation, made from pulverized coral dust mixed and bonded with plastic resins. While chemically similar to genuine coral, this material lacks the characteristic fibrous, wood-grain structure seen in solid, natural pieces. Observing the surface for this lack of organic texture helps differentiate reconstituted material from solid coral.
Simple At-Home Verification Techniques
A magnification check is effective for verifying authenticity. Using a jeweler’s loupe, ideally 10x power or higher, look for the fine, fibrous, microscopic structure of the coral skeleton. This unique, minute grain pattern is virtually impossible to replicate in fakes.
The temperature and weight of the piece offer immediate clues to its identity. Genuine coral is a poor thermal conductor and will feel cool against the skin, warming very slowly as it is held. Conversely, plastic or resin imitations warm up almost instantly to body temperature.
A gentle friction test can be performed by rubbing the piece against an unglazed ceramic surface, such as the bottom of a porcelain plate. Authentic coral will produce a white or very pale pink powder streak, while many dyed fakes leave a distinctly colored red streak. Perform this test lightly and on an inconspicuous area to avoid damage. The density of the coral can be assessed by comparing the item’s weight to known genuine pieces.
When to Seek Expert Confirmation
For pieces representing a significant financial investment or considered antiques, seek professional confirmation from a certified gemologist. Experts possess the necessary equipment to conduct definitive, non-visual analysis. The ultimate proof involves microscopic cross-section analysis, confirming the unique skeletal structure and ruling out foreign bonding agents.
Professionals can also perform chemical tests, such as applying a mild acid like lemon juice to an unseen spot. Since coral is primarily calcium carbonate, a genuine piece will react by effervescing or bubbling slightly, releasing carbon dioxide. A gemological certificate, often obtained through advanced methods like X-ray diffraction or specific gravity testing, provides the highest level of assurance regarding the material’s origin and treatment status.