Favosites fragment (Honeycomb Coral fragment)
Favosites cf. alpenensis • Body fossil, colonial invertebrate
Geological Period
Devonian Period
Estimated Age
360 - 419 million years
Preservation Type
Recrystallization and silicification (common for Michigan 'Petoskey-style' tabulate corals); original calcium carbonate has been replaced by silica or calcite.
Condition Assessment
Fair to Poor (as a specimen); though it has a nice polish from natural wave action, it is highly eroded and lacks clear, distinct corallite walls.
Taxonomic Classification
Phylum: Cnidaria, Class: Anthozoa, Order: Tabulata, Family: Favositidae, Genus: Favosites
Morphological Description
A water-worn fragment showing a cross-section of polygonal, hexagonal corallites (individual coral chambers). The interior structures (septa and tabulae) appear partially dissolved or recrystallized, leaving a mottled, semi-translucent appearance.
Rock Matrix
Minimal matrix remaining as this is a beach-worn pebble; likely originated from a Devonian limestone or shale bedrock.
Formation & Location
Potentially from the Traverse Group or Dundee Limestone. Commonly found along the shores of Lake Erie and Lake Michigan, specifically sterling State Park (Monroe, MI).
Size & Dimensions
Approximately 2-3 cm; consistent with typical small, eroded fragments found in beach gravels.
Value & Rarity
Estimated Market Value
$1 - $5 USD
Auction Estimate
N/A (Generally sold in bulk lots/small gravel samples rather than individual auction lots)
Rarity Assessment
Common; these fragments are widely distributed in the glacial till and Great Lakes beach sediments of Michigan.
Scientific Significance
Provides evidence of the warm, shallow tropical seas that covered Michigan during the Devonian. Illustrates the diversity of tabulate corals before their extinction at the end of the Permian.
Preparation Recommendations
No heavy preparation required. Can be polished further with a lapidary rock tumbler or preserved with a light coat of mineral oil to enhance the internal patterns.
Notable Features
The high degree of natural polishing gives it a pearl-like, nacreous sheen in certain areas, likely due to the specific mineral replacement in the Monroe, MI region.
Notes
Found at Sterling State Park Michigan.