Coral

Coral is the skeletal remains of marine invertebrates - tiny colonial animals called polyps that secrete calcium carbonate to build branching, tree-like structures on the ocean floor. Precious coral (the gem variety, primarily Corallium rubrum and related species) grows extremely slowly - roughly 1 millimeter per year - in deep Mediterranean and Pacific waters at depths of 50-300 meters.

The red color that makes precious coral so valuable comes from carotenoid pigments incorporated into the calcium carbonate skeleton. The deeper the red (called 'ox blood' or 'moro'), the more valuable the material. 'Angel skin' coral - a delicate pale pink - is the second most valued variety.

Coral is now one of the most ethically complicated gems. Mediterranean coral populations have been devastated by centuries of harvesting. International regulations (CITES) restrict trade in many coral species. The intersection of gem value, marine conservation, and indigenous cultural practices (coral is sacred in many Pacific Island and Native American traditions) creates ongoing tension. Sustainable harvesting is possible but enforcement is difficult.

Precious coral is identified by its organic branching structure, warm red-to-pink color, waxy luster, and the fine parallel growth lines visible on the surface when examined under magnification. At hardness 3.5, it's quite soft.

Distinguish from dyed bamboo coral (much cheaper, larger pieces, uniform color), glass imitations (no organic structure, may have bubbles), and plastic (too light, warm to touch, no growth lines). Genuine precious coral has a distinctive fine-grained texture and organic feel that imitations don't replicate.