Modern Freshwater Mussel Fragment (Commonly mistaken for a fossil)
Likely a member of the Unionidae family, such as Lampsilis cf. siliquoidea (Fatmucket) or similar Great Lakes freshwater mussel species • Body fossil (sub-fossil or modern biological remains); Invertebrate bivalve mollusk
Geological Period
Holocene / Recent
Estimated Age
0-10,000 years (likely decades to centuries old)
Preservation Type
Unaltered biological remains; not mineralized or petrified. The presence of original nacre and organic surface layers indicates a modern or sub-fossil specimen.
Condition Assessment
Fair; partial specimen only. Shows signs of physical weathering (taphonomic wear) from wave action and mechanical breakage.
Taxonomic Classification
Phylum: Mollusca, Class: Bivalvia, Order: Unionida, Family: Unionidae
Morphological Description
Fragmentary bivalve shell showing a curved marginal outline with distinct concentric growth lines. The interior displays a nacreous (mother-of-pearl) luster, while the exterior shows remaining periostracum (organic coating) in brownish bands.
Rock Matrix
None. The specimen is a loose shell fragment typically found in beach sand or lacustrine sediment.
Formation & Location
Found at Sterling State Park, Michigan; likely originating from the modern benthos of Lake Erie or nearby drainage basins.
Size & Dimensions
Approximately 25-40mm in length for this fragment; consistent with medium-to-large freshwater mussels common to the Great Lakes region.
Value & Rarity
Estimated Market Value
$0 - $2 USD
Auction Estimate
Negligible / Not suitable for natural history auctions
Rarity Assessment
Common; freshwater mussel fragments are ubiquitous along Michigan shorelines and the Great Lakes.
Scientific Significance
Low scientific significance as a fossil; however, it serves as a bioindicator for modern freshwater ecosystem health and recent malacology in the Great Lakes.
Preparation Recommendations
No paleontological preparation needed. Can be cleaned with mild soap and water. If intended for study, prevent desiccation which can cause the nacreous layers to flake/delaminate.
Notable Features
The most notable feature is the high-quality iridescent nacre on the interior surface and its typical beach-worn appearance, which often causes beachcombers to confuse these with ancient fossils despite their modern origin.
Notes
Found at Sterling State Park in Michigan