Precious Coral
Corallium rubrum (organic calcium carbonate) · Organic Gem
Crystal System
Orthorhombic (Aragonite crystal system, though organic structure is typically branching or massive)
Mineral Group
Carbonates (Biogenic organic mineraloid)
Chemical Formula
CaCO3 (Calcium Carbonate with organic matrix and trace carotenoids)
Formation Process
Biogenic formation in marine environments by colonies of marine invertebrates (octocorals) secreting a skeleton of calcium carbonate in warm, deep ocean waters
About This Crystal
The specimen is a smooth, polished cabochon with a vibrant orange-red to salmon color, showcasing an opaque transparency with a vitreous to waxy luster when polished, typical of precious coral jewelry components
Physical Characteristics
Color ranges from deep red to pale pink and orange; white streak; no cleavage; uneven to conchoidal fracture; specific gravity around 2.60 to 2.70; brittle tenacity; reactive to acids due to carbonate composition
Optical Properties
Biaxial negative with refractive indices typically around 1.486 to 1.658; usually opaque showing no significant pleochroism or other advanced optical phenomena aside from a smooth surface polish reflection
Hardness & Durability
Origin Region
Mediterranean Sea, Red Sea, waters around Japan, Taiwan, and Midway Atoll
Hardness & Durability
Mohs hardness of 3.5 to 4; poor toughness due to porous organic-mineral structure; sensitive to acids, perspiration, cosmetics, and heat; poor durability for everyday heavy-wear rings without protective settings
Care & Maintenance
Clean only with a soft, damp cloth and mild soap; avoid ultrasonic cleaners, steam, harsh chemicals, acids, perfumes, and prolonged exposure to direct sunlight or extreme heat
Rarity & Value
Rare and increasingly protected due to over-harvesting and environmental regulations; value determined by color uniformity, size, lack of blemishes, and species origin; treated with dyeing or impregnation in lower qualities
Special Characteristics
Biogenic organic origin, featuring subtle internal growth lines or minute microscopic canals characteristic of natural coral skeletal structures
Lore & History
Used since ancient Egyptian, Roman, and prehistoric times as a protective amulet against evil spirits, misfortune, and illness; traditionally associated with the root chakra, vitality, emotional healing, and passion in modern crystal lore