Rugose Coral Colony / Colonial Coral Fossil
Colonial rugose or tabulate coral cf. Hexagonaria or Favosites sp. • Body fossil, invertebrate colonial coral
Geological Period
Devonian to Carboniferous
Estimated Age
350 to 400 million years old
Preservation Type
Silicification and calcitic replacement with secondary iron oxide staining (limonite/hematite patina)
Condition Assessment
Good condition; weathered exterior surface showing moderate abrasion and iron-staining, but structural integrity of the corallites remains largely intact
Taxonomic Classification
Phylum: Cnidaria, Class: Anthozoa, Order: Rugosa or Tabulata, Family: Various, Genus: Various colonial forms
Morphological Description
Massive colonial coral head exhibiting numerous tightly packed corallites with visible radial septa and skeletal walls, forming a honeycombed or rugose textured surface structure.
Rock Matrix
Weathered limestone and calcareous mudstone matrix with surface iron oxidation
Formation & Location
Devonian limestone formations worldwide, commonly found in the Midwest and Eastern United States (e.g., Jeffersonville Limestone, Dundee Limestone)
Size & Dimensions
Approximately 8 to 10 cm across, fitting well within the typical hand-sample size range for coral colonial heads
Value & Rarity
Estimated Market Value
$15 to $45 USD
Auction Estimate
$20 to $50 USD
Rarity Assessment
Common, widely distributed across Paleozoic marine strata globally
Scientific Significance
Provides valuable data on ancient shallow-marine tropical paleoenvironments, reef ecosystems, and historical marine biodiversity during the Paleozoic era
Preparation Recommendations
Gentle mechanical cleaning with a soft brush to remove loose surface dirt; optional mild acid etching if further internal micro-structure exposure is desired, followed by storage in a dry environment
Notable Features
Distinctive honeycombed coral calices filled with yellowish-brown iron oxide weathering crusts, highlighting the intricate skeletal architecture