Colonial Rugose Coral (Honeycomb Coral or Star Coral)
Lithostrotion cf. vorticale or Siphonodendron species • Body fossil; Invertebrate (Cnidaria); Colonial Coral
Geological Period
Carboniferous Period (likely Mississippian/Pennsylvanian subtypes)
Estimated Age
299 to 359 million years
Preservation Type
Recrystallization with replacement by calcite or silica; the original aragonite/calcite skeletal structure has been replaced by more stable minerals.
Condition Assessment
Good; the specimen shows clear surface detail of the corallites, though it is a partial colony fragment with some weathered edges and matrix obscuring the base.
Taxonomic Classification
Phylum: Cnidaria, Class: Anthozoa, Order: Stauriida (Rugosa), Family: Lithostrotionidae, Genus: Lithostrotion (cf.)
Morphological Description
A massive, cerioid colonial structure. Individual corallites are closely packed and hexagonal to sub-polygonal in shape. Visible radiating septa (lines) converge toward the center of each corallite, giving it a floral or star-like surface texture.
Rock Matrix
Dense, dark grey / carbonaceous limestone or fine-grained calcilutite, indicative of a marine shelf environment.
Formation & Location
Commonly found in the Carboniferous Limestones of the United Kingdom (e.g., Derbyshire, Yorkshire) or the Mississippian-aged formations of the United States (e.g., St. Louis Limestone).
Size & Dimensions
Approximately 8-10 cm in length; corallites are typically 4-7 mm in diameter, which is standard for this genus.
Value & Rarity
Estimated Market Value
$25 - $45 USD
Auction Estimate
$20 - $50 USD
Rarity Assessment
Common; corals of this type are widely distributed and abundant in Carboniferous marine deposits globally.
Scientific Significance
Rugose corals were major reef-builders of the Paleozoic. This specimen provides evidence of shallow, warm, clear tropical marine environments and helps date the strata to the Carboniferous era.
Preparation Recommendations
Mechanical preparation with a pneumatic scribe could reveal more of the colony structure. Surface can be cleaned with water and a soft brush; avoid acids which will dissolve the limestone matrix.
Notable Features
The specimen exhibits a well-preserved 'cerioid' growth habit where corallites share walls, creating the distinctive honeycomb appearance on the weathered surface.