Favosites (Honeycomb Coral Fossil)
Favosites gothlandicus · Fossilized Mineral Specimen
Crystal System
Hexagonal symmetry (within the corallite structure); massive habit
Mineral Group
Carbonates (Calcite group)
Chemical Formula
CaCO3 (primarily Calcite or Aragonite replacement)
Formation Process
Sedimentary/Permineralization: The original organic skeletal structure was replaced by calcite or silica from mineral-rich groundwater during burial.
About This Crystal
A grayish-tan colonial coral fossil featuring a distinct honeycomb pattern of polygonal pores (corallites). It exhibits a dull to waxy luster and translucent to opaque diaphaneity.
Physical Characteristics
Color: Gray, tan, or brown. Streak: White. Cleavage: Perfect rhombohedral (in calcite areas). Specific Gravity: 2.7. Fluorescence: Often shows weak red or orange under LWUV.
Optical Properties
Usually displays double refraction in crystallized calcite sections; localized pearly luster on weathered surfaces.
Hardness & Durability
Origin Region
Michigan (Petoskey area), New York, and Ohio, USA; also Gotland, Sweden. Formed in shallow marine shelf environments.
Hardness & Durability
Mohs Hardness: 3 (soft). Brittle tenacity. Low durability for jewelry; easily scratched by steel.
Care & Maintenance
Avoid acids (vinegar, lemon juice) as they will dissolve the carbonate. Clean with a soft brush and lukewarm water. Store away from harder minerals.
Rarity & Value
Common; widely available in Devonian and Silurian limestone deposits. Value is generally low ($5-$30 for hand samples).
Special Characteristics
Polygonal 'honeycomb' structure with visible horizontal walls (tabulae) inside the tubes.
Lore & History
An extinct genus from the Ordovician to Devonian periods. Historically used as decorative stones. Metaphysically associated with grounding and longevity.