White Coral
Aragonite or Calcite var. Scleractinia (Coral) · Organic Gem / Marine Mineral Specimen
Crystal System
Orthorhombic or Trigonal (Microcrystalline structure within a branching biological habit)
Mineral Group
Carbonates (Aragonite Group)
Chemical Formula
CaCO3 (Calcium Carbonate with trace Magnesium and organic matter)
Formation Process
Biogenic / Sedimentary: Secreted by marine polyps (Scleractinia) to form a stony exoskeleton through the precipitation of calcium carbonate from seawater.
About This Crystal
White, branching skeletal structure with a matte to sub-vitreous luster. The surface features small pores or 'theca' where polyps once resided. It is opaque with a snowy white color, often exhibiting a porous, bone-like appearance.
Physical Characteristics
Color: White; Streak: White; Cleavage: None (organic structure); Fracture: Splintery to uneven; Specific Gravity: 2.6 - 2.7; Fluorescence: Often weak white or violet under UV light.
Optical Properties
Refractive Index: 1.486 - 1.658; Birefringence: High (0.172); Optical Character: Uniaxial or Biaxial negative; Phenomenon: None (opaque).
Hardness & Durability
Origin Region
Tropical and subtropical marine environments; notable sources include the Indo-Pacific, Great Barrier Reef, and the Mediterranean.
Hardness & Durability
Mohs Hardness: 3.5 - 4.0; Toughness: Poor to fair; Stability: Sensitive to heat, acids, and extended sun exposure which can cause brittleness.
Care & Maintenance
Clean only with a soft, damp cloth and very mild soapy water if necessary. Avoid ultrasonic cleaners, steam, and acids (including perfumes/hairspray). Store in a soft pouch away from harder gemstones to prevent scratching.
Rarity & Value
Common globally but increasingly regulated due to environmental protections; value depends on the intricacy of the branching and lack of damage. Common treatments include bleaching or resin impregnation.
Special Characteristics
Features a unique 'tree-like' or fan-shaped growth habit known as dendritic arborescence. It is highly porous and sensitive to pH changes.
Lore & History
Historically used as an amulet against the 'evil eye' and to prevent hemorrhaging. In traditional lore, it is associated with the Base and Heart chakras, representing modesty, wisdom, and connection to the element of water.