Pyritized Gomphocladivm or 'Pine-cone' Fossil
cf. Gomphocladivm or inorganic Pyrite Nodule • Body fossil (pseudofossil-mimic); broadly classified as a pyritized marine invertebrate mass or seed-cone mimic
Geological Period
Lower Jurassic (Toarcian)
Estimated Age
180 - 185 million years
Preservation Type
Pyritization (replacement and recrystallization by iron disulfide/pyrite)
Condition Assessment
Good; showing well-defined crystalline structure with typical brassy metallic luster, though exhibiting slight peripheral surface oxidation
Taxonomic Classification
Phylum: Porifera (Sponges) or Pseudofossil; Class: Unknown (likely Geodia-type sponge or Inorganic nodule); Genus: cf. Gomphocladivm
Morphological Description
Globular, sub-spherical shape with a distinct mammillated surface composed of interlocking cuboidal or octahedral pyrite crystals. The surface exhibits a repeating geometric pattern resembling a pine cone or blackberry.
Rock Matrix
Associated with Posidonia Shale or similar anoxic marine mudstones; the matrix is largely absent but likely black shale
Formation & Location
Likely Posidonienschiefer (Posidonia Shale) of Holzmaden, Germany, or the Jurassic Coast of Dorset, England
Size & Dimensions
Approximately 2.5 - 4 cm in diameter; typical for small pyritized nodules or sponge fossils found in Toarcian deposits
Value & Rarity
Estimated Market Value
$15 - $45 USD
Auction Estimate
$20 - $60 USD (as part of a natural history group lot)
Rarity Assessment
Uncommon; while pyrite nodules are common, the distinct 'cone' morphology of these biological mimics is sought after by niche collectors
Scientific Significance
Demonstrates specific diagenetic processes in anoxic environments where sulfate-reducing bacteria facilitate the replacement of organic structures with pyrite
Preparation Recommendations
Must be kept in low humidity (under 45%) to prevent pyrite disease (oxidation into sulfuric acid). Treat with Paraloid B-72 if decay is detected.
Notable Features
Remarkable geometric symmetry that mimic a botanical seed cone despite its likely marine sponge or inorganic origin