Fossil Sea Urchin (Echinoid Flint Internal Mold)
Echinocorys sp. or Micraster sp. (Internal flint cast) • Body fossil / Internal mold (steinkern), Invertebrate
Geological Period
Late Cretaceous (Campanian to Maastrichtian)
Estimated Age
66 to 83 million years
Preservation Type
Internal mold / Replacement by microcrystalline quartz (flint/chert steinkern)
Condition Assessment
Fair to Good. Weathered and beach-rolled with smoothed surfaces, but essential suture traces and general heart-like form remain intact.
Taxonomic Classification
Phylum Echinodermata, Class Echinoidea, Order Spatangoida or Holectypoida, Family Micrasteridae / Galeritidae
Morphological Description
Sub-globular, heart-shaped or dome-shaped rounded pebble composed of chert/flint, showing dark suture-like lines corresponding to the ambulacral grooves and interambulacral plate boundaries of a regular or irregular echinoid test.
Rock Matrix
Flint / Chert pebble, originally formed within Chalk matrix
Formation & Location
Chalk Group (e.g., White Chalk Subgroup), commonly found as eroded flint pebbles on beaches or glacial till in Northwest Europe (UK, Netherlands, Belgium, Northern France, Denmark, Germany)
Size & Dimensions
Approximately 4 - 6 cm in diameter, typical for medium-sized Cretaceous irregular echinoids
Value & Rarity
Estimated Market Value
$5 - $20 USD
Auction Estimate
$10 - $25 USD
Rarity Assessment
Common (frequently found in Cretaceous chalk deposits and coastal beaches of Northwest Europe)
Scientific Significance
Illustrates the process of silica replacement within marine chalk environments during the Cretaceous period, providing diagnostic information on echinoid anatomy via internal casts.
Preparation Recommendations
No mechanical preparation required. Keep clean with gentle soap and water, avoid acid cleansers which could dull quartz luster, and display in a dry environment.
Notable Features
Distinctive dark ambulacral star-pattern preserved in pale translucent flint, created by silica infilling the empty echinoid shell before the shell itself dissolved.
Notes
Northwest europe