Stromatolite (Cyanobacterial Mat)
Collenia or Cryptozoon aff. (specific identification requires thin-section analysis) • Trace fossil and organosedimentary structure; Microfossil/Bacterial origin
Geological Period
Precambrian (likely Proterozoic eon)
Estimated Age
600 to 2,500 million years
Preservation Type
Replacement and permineralization (silicified or iron-enriched)
Condition Assessment
Good (partial specimen); displays visible lamination but lacks the external weathered 'cabbage head' morphology found in complete heads.
Taxonomic Classification
Domain: Bacteria, Phylum: Cyanobacteria (Blue-green algae)
Morphological Description
Distinctive laminated or layered structure consisting of alternating light and dark bands. The specimen shows wavy, slightly convex upward doming of microbial layers, characteristic of benthic cyanobacterial growth patterns.
Rock Matrix
Ferruginous (iron-rich) chert or siltstone; show signs of hematite or limonite staining resulting in the reddish-orange hue.
Formation & Location
Common in the Gunflint Chert (USA/Canada), Bitter Springs Formation (Australia), or similar Proterozoic sedimentary basins.
Size & Dimensions
Approximately 4-6 cm in width; representative of a small hand-specimen fragment from a larger reef structure.
Value & Rarity
Estimated Market Value
$15.00 - $35.00 USD
Auction Estimate
$20.00 - $50.00 USD (as part of a bulk natural history lot)
Rarity Assessment
Common (globally widely distributed in Proterozoic and Archean strata, though specific high-grade banded iron formations are highly collected).
Scientific Significance
Crucial for understanding the Oxygenation Event; provides evidence of early life and photosynthetic activity which transformed the Earth's atmosphere.
Preparation Recommendations
Low maintenance; can be cut and polished on one face to better reveal the cross-sectional laminations. Store in a dry environment to prevent further iron oxidation.
Notable Features
The specimen exhibits high iron content, giving it a distinctive 'banded iron' appearance often associated with the early periods of Earth's crustal development.