Fossilized Stromatoporoid or Sponge
Stromatoporoidea indet. • Body fossil / Invertebrate
Geological Period
Silurian to Devonian
Estimated Age
443 to 359 million years old
Preservation Type
Permineralization and complete silicification or calcification within a carbonate matrix
Condition Assessment
Good condition with a weathered, water-worn exterior obscuring finer internal micro-structures
Taxonomic Classification
Phylum Porifera, Class Demospongiae, Order Stromatoporida
Morphological Description
Rounded, nodular morphology with visible fine concentric laminae and vertical pillars forming a reticulate internal skeletal structure. The outer surface shows pitting and a banded pattern.
Rock Matrix
Silicified limestone or calcareous rock matrix
Formation & Location
Found globally in marine shelf carbonate environments, commonly in the Midwest United States and Gotland, Sweden
Size & Dimensions
Approximately 4 to 6 centimeters in diameter, typical for smaller nodular reef-building organisms
Value & Rarity
Estimated Market Value
10 to 30 USD
Auction Estimate
15 to 40 USD
Rarity Assessment
Common, frequently found in Paleozoic marine deposits
Scientific Significance
Important indicator of ancient shallow marine reef environments and tropical shelf paleoecology during the Paleozoic era
Preparation Recommendations
No intensive preparation needed; gentle washing with water and a soft brush to remove surface dirt, stored in a dry environment
Notable Features
Distinct water-worn smooth side contrasting with the porous, banded growth structure on the upper surface indicating wave action rounding