Bryozoan colony (likely Cyclostome or Trepostome)
Indeterminate Bryozoan; cf. Hallopora or aff. Monticulipora • Body fossil (Replacement/Mineralization), Invertebrate
Geological Period
Upper Ordovician (Cincinnatian)
Estimated Age
444 to 450 million years
Preservation Type
Mineral replacement and permineralization. The green color mentioned suggests the presence of glauconite or potentially chlorite/epidote mineralization within the pores.
Condition Assessment
Fair to Good. The specimen is heavily water-worn (tumbled), which has polished the surface but obscured finer diagnostic features like monticules or acanthopores.
Taxonomic Classification
Phylum: Bryozoa; Class: Stenolaemata; Order: Trepostomatida (tentative); Family: Unknown
Morphological Description
Specimen shows a dense network of calcified tubular structures (zooecia) typical of colonial bryozoans. The surface exhibits a mesh-like or 'lacey' pattern of fine lines representing the individual housing chambers of the colony members. The general shape is sub-rounded, likely eroded by water transport.
Rock Matrix
Silicified limestone or calcarenite matrix typical of the Whitewater or Saluda Formations in Indiana. Surface shows high water-polish (river worn).
Formation & Location
Cincinnatian Series (Whitewater Formation), Brookville, Indiana, USA.
Size & Dimensions
Approximately 4-6 cm in diameter; consistent with common stream-tumbled bryozoan fragments from this region.
Value & Rarity
Estimated Market Value
$5.00 - $15.00 USD
Auction Estimate
$10.00 - $25.00 USD (typically sold in bulk lots for this quality)
Rarity Assessment
Common. Bryozoans are among the most abundant fossils found in the Brookville/Cincinnatian area.
Scientific Significance
Provides evidence of the diverse 'Bryozoan Meadows' that existed in the shallow epicontinental seas of the Ordovician Period in what is now the midwestern United States.
Preparation Recommendations
Keep as a 'pocket stone' or display as a natural river-polished specimen. No further mechanical preparation is required. Avoid acidic cleaners which may dissolve the carbonate structure.
Notable Features
The specimen exhibits a high natural polish due to fluvial (river) action. The 'gem-like' green appearance when wet is a classic indicator of mineral replacement in high-silica or glauconitic environments.
Notes
found in brookville indiana. it is very green when wet. thought it might be a gem.