Coral (Precious Coral)

Hardness: 2.5-4.5 on the Mohs scale (relatively soft). Color: Varies widely, often white, cream, pink, orange, red, blue, purple, black, or brown. Luster: Waxy to pearly. Crystal Structure: Amorphous (lacks a defined crystal structure). Cleavage: None. Specific Gravity: 2.60-2.85.

Coral polyps, tiny marine invertebrates, secrete calcium carbonate (aragonite or calcite) to form hard external skeletons. Over many years, these skeletal structures accumulate to create large coral colonies or reefs. Precious corals, like those used in jewelry, grow in deep, dark waters (30 to 300 meters deep) with low sediment, rather than in shallow, sunlit reefs. Their geological age can range from recent to many thousands of years old, depending on the growth and accumulation rate.

Primarily used as a gemstone in jewelry, including beads, cabochons, carvings, and inlays. Its vibrant colors make it a popular material for decorative objects and sculptures. Historically, it has also been used for medicinal purposes in various cultures.

Coral is unique among gemstones as it is formed by living organisms. Red coral has been highly prized since ancient times and was used for adornment and in rituals. Due to overharvesting and environmental factors, many coral species are now endangered or protected, making modern harvesting of precious coral illegal in many areas. Much of the coral sold today is farmed or reproduced via sustainable methods, or is antique/vintage. The 'eye' visible in some coral forms is not an eye but the opening where polyps extended.

In the field (or when identifying raw material), coral is identified by its branching, tree-like structure (though finished pieces are often polished and shaped like the image). Its characteristic growth rings can sometimes be seen in polished specimens. It is relatively soft and can be scratched by a knife. Natural coral may have small pores or channels visible, which are remnants of the polyp structure. It's commonly found in tropical and subtropical waters around the world, particularly in the Mediterranean Sea, Red Sea, off the coast of Japan, Taiwan, and Hawaii. For collectors, distinguishing natural, untreated coral from dyed or imitation materials is crucial. Examine color consistency, presence of natural imperfections, and specific gravity. The sample in the image appears to be a polished, possibly tumbled, piece of coral, likely a cream or salmon color, given its smooth, uniform, and slightly waxy appearance, consistent with polished coral used in jewelry or decorative items.