Agatized Fossil Coral
Quartz var. Agatized Coral (Replacement of Anthozoa) · Semi-Precious Gemstone / Fossilized Mineral Specimen
Crystal System
Trigonal/Hexagonal crystal system (Microcrystalline); typical habit is massive, replacing the original radial and tabulate structures of coral polyps.
Mineral Group
Silicates (Subgroup: Tectosilicates / Silica Group)
Chemical Formula
SiO2 (Silicon Dioxide) with trace impurities of Iron (Fe), Manganese (Mn), and Carbonates (CaCO3)
Formation Process
Pseudomorphosis / Hydrothermal Replacement: Originally calcium carbonate coral skeletons are buried in silica-rich groundwater, where the silica gradually replaces the carbonate over millions of years while preserving the organic structure.
About This Crystal
Spherical polished specimen displaying a tan, cream, and brownish color palette. It features visible 'flower' or 'star' patterns which represent the cross-sections of ancient coral polyps. Luster is vitreous to waxy, and transparency ranges from opaque to translucent in silicated areas.
Physical Characteristics
Color: Cream, beige, and brown; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.60–2.64; Fluorescence: May show dull yellow or green under LWUV depending on trace minerals.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; Optical Phenomenon: Patterned appearance due to preservation of septa and corallites; no significant pleochroism.
Hardness & Durability
Origin Region
Notable sources include Florida and Georgia (USA), Indonesia (Sumatra), and Morocco; typically found in limestone-rich marine sedimentary basins.
Hardness & Durability
Mohs Hardness: 6.5 to 7; High toughness and excellent durability for jewelry or decorative use, as it is composed of chalcedony quartz.
Care & Maintenance
Safe to clean with warm soapy water and a soft brush. Avoid harsh chemicals or acids which might react with any leftover carbonate patches. Store separately from softer stones to avoid scratching them.
Rarity & Value
Moderately common, but high-quality specimens with intact floral patterns are valued by collectors. Prices range from $10 to $100+ depending on size and pattern definition; usually untreated.
Special Characteristics
Displays distinct 'flower' patterns of extinct coral species (such as Favosites). It is a unique bridge between the animal and mineral kingdoms, classified as a pseudomorph.
Lore & History
Ancient Greeks believed coral protected against evil and sea-terrors. Metaphysically, it is associated with grounding and longevity due to its millions of years of fossilization. It is often linked to the Root and Solar Plexus chakras.