Dinosaur Gastrolith
Indeterminate dinosaurian gastrolith (gastrolith ichnofossil) • Trace fossil, vertebrate stomach stone
Geological Period
Cretaceous or Jurassic
Estimated Age
66 to 145 million years
Preservation Type
Original silicified rock mineralogy with mechanical rounding and polish acquired via gastral milling (bio-polishing)
Condition Assessment
Very Good, showing classic natural polish, stable mineral composition, and no active fracturing
Taxonomic Classification
Ichnotaxon, non-avian Dinosauria
Morphological Description
Polished, rounded, sub-angular to well-rounded pebbles exhibiting smooth surfaces with characteristic impact pits, polish from stomach action, and reddish-brown to dark banded chert or quartzite coloration.
Rock Matrix
None attached directly; individual clasts are composed of dense, cryptocrystalline quartz (chert/jasper)
Formation & Location
Morrison Formation (USA) or Cloverly Formation, commonly found in western North America
Size & Dimensions
Approximately 2 to 4 cm in length per specimen, consistent with medium-sized herbivorous dinosaur gizzard stones
Value & Rarity
Estimated Market Value
$20 to $50
Auction Estimate
$15 to $40
Rarity Assessment
Common
Scientific Significance
Provides evidence of digestive physiology and dietary mechanical processing in herbivorous dinosaurs, as well as behavioral migration and geophagy
Preparation Recommendations
No further mechanical preparation needed; store in a stable, low-humidity environment inside a secure display case
Notable Features
High glossy natural polish resulting from prolonged churning in a dinosaurian gizzard combined with contrasting dark bands within the reddish-brown matrix