With its bold hues and oceanic origins, coral is a vibrant and valuable addition to a jewellery or sculpture collection. It's often used in intricate jewellery designs and ornate works of art because the soft mineral composition makes it suitable for carving. However, real coral is extremely rare and over-harvesting has endangered many forms of coral, including black coral. Strict regulations have also limited the amount of coral available to consumers. Coral's beauty and rarity has lead to a flurry of imitations, and telling the real from the fake requires knowledge and skill.
Run your fingers around coral beads and carvings, checking for sharp ridges or bumps. Real coral should be completely smooth and polished, with no seam marks.
A ridge running around the circumference of a coral bead is an indication that the bead was created in a mould and is most likely plastic.
Glass coral beads may have a small, sharp point near the hole, where glass beads were either snipped from a rod of molten glass or from where the dot of glass was formed.
Do a small scratch test to determine the hardness of your coral. Coral is a fairly soft mineral, rating a three to four on the Mohs Scale of Hardness. Glass, which is commonly used to imitate coral, is harder than the real thing with a rating between five and six. Gently rub a corner of your coral on a small piece of plate glass (not the other way around, or you will damage the coral). If the glass is scratched, then your coral is likely made of glass. If there is no impact, you are likely dealing with real coral.
Compare the weight of your piece of coral and a piece of fake coral, if you have one, of a similar size. Real coral is significantly heavier than imitations. There should be a feeling of density and weight when real coral is held in your hand that plastic and glass cannot replicate. If your coral feels light or is not heavier than the fake coral, then your coral is an imitation.
Inspect your coral under a very bright light, using a device such as a professional jeweller's loupe that will give you 10x magnification. Coral will have a series of fine, interconnected lines running through it, forming a cross-grain similar to that of ivory. If these lines are present, your coral is most likely authentic.
Consider the context of your coral piece. Real coral is typically mounted in expensive settings like gold and silver. This expense is rarely wasted on a glass or plastic imitation. The strict laws that govern coral harvesting also makes real coral rare, so be prepared to pay handsomely, even for vintage pieces. If your coral cost £12.90, for example, it is most likely a fake.