CORAL

Organic gem from marine invertebrate skeletons (primarily calcium carbonate in various coral species), not mineral, but valued in jewelry.
Coral Varieties:
Precious Corals --> Red, Pink, and Orange (Corallium deep-sea-coral)—dense, fine-grained, glossy when polished.
Black Coral --> Proteinaceous skeleton, jet-black to dark brown; durable carvings and beads.
Blue Coral --> Heliopora coerulea, blue-gray aragonite; often stabilized for jewelry.
White Coral --> Milky to creamy; “angel skin” variants; often bleached or dyed.
Tube/Bamboo Coral --> Segmented, tubular structures from deep or shallow species