Stromatolite (Cyanobacterial Mat)
Collenia species (cf. Collenia brownii or similar laminate form) • Trace fossil (Biogenic Sedimentary Structure); Microorganism-driven
Geological Period
Precambrian (likely Proterozoic eon)
Estimated Age
500 to 2,500 million years
Preservation Type
Recrystallization and mineralization with significant iron oxide staining
Condition Assessment
Fair to Good; the internal structure is weathered and the specimen appears to be a fractured piece rather than a complete head, but the diagnostic layering is still visible.
Taxonomic Classification
Domain: Bacteria, Phylum: Cyanobacteria (formerly blue-green algae)
Morphological Description
Exhibits characteristic fine, undulating laminae (layers) and a domal or stratiform growth pattern. The surface shows rugose, bumpy textures consistent with microbial mat accumulation and sediment trapping.
Rock Matrix
Ferruginous chert or silicified dolostone with hematite and limonite inclusions giving it a reddish-brown color.
Formation & Location
Possible origin include the Gunflint Chert (Ontario/Minnesota) or the Bitter Springs Formation (Australia). Common in iron-rich Precambrian formations.
Size & Dimensions
Approximately 8-10 cm in width; typical for a hand-sized section of a larger microbial reef.
Value & Rarity
Estimated Market Value
USD $15.00 - $35.00
Auction Estimate
USD $20.00 - $50.00 (usually sold in bulk lots for educational purposes)
Rarity Assessment
Common; stromatolites are globally distributed in Precambrian strata, though well-articulated, polished specimens from specific locations command more interest.
Scientific Significance
Stromatolites represent the earliest evidence of life on Earth. They are responsible for the 'Great Oxygenation Event' via photosynthesis, fundamentally altering Earth's atmosphere.
Preparation Recommendations
Sectioning and polishing one side is recommended to reveal the internal laminar structure. Keep in a dry environment to avoid further oxidation of iron minerals.
Notable Features
Distinctive reddish-ochre coloration suggesting high iron content in the paleoenvironment, likely representing a Banded Iron Formation (BIF) associated microbial community.