Trilobite (Internal Mold Fragment)
Redlichia cf. chinensis or similar Olenellid/Redlichiid species • Body fossil; internal natural mold of an invertebrate arthropod
Geological Period
Cambrian to Ordovician
Estimated Age
485 - 510 million years
Preservation Type
Internal mold within an iron-rich (ferruginous) sedimentary matrix; secondary replacement with hematite or limonite is likely.
Condition Assessment
Fair; the specimen is fragmentary, lacking a cephalon (head) and pygidium (tail). The surface detail is weathered.
Taxonomic Classification
Phylum: Arthropoda, Class: Trilobita, Order: Redlichiida (possible)
Morphological Description
The specimen shows partial thoracic segments and a portion of the pleural lobes. Convexity of the segments is visible, indicating a natural internal mold of the exoskeleton. Faint transverse grooves signify segment boundaries.
Rock Matrix
Ferruginous siltstone or ironstone, characterized by a deep reddish-orange/ochre color due to High iron oxide content.
Formation & Location
Likely the Mantou Formation of China (Shandong or Shanxi provinces) or equivalent Cambrian 'Red Beds' globally.
Size & Dimensions
Approximately 4-6 cm in width; represents a medium-sized trilobite specimen for this geological period.
Value & Rarity
Estimated Market Value
$10 - $25 USD
Auction Estimate
$15 - $30 USD
Rarity Assessment
Common; fragments of this type are frequently found in massive numbers in Cambrian siltstones.
Scientific Significance
Provides evidence of early Paleozoic marine life and the diversification of arthropods in high-iron depositional environments.
Preparation Recommendations
Keep dry to prevent oxidation of iron minerals. Use a soft brush for cleaning; mechanical air-scribing is not recommended due to the soft, crumbly nature of the matrix.
Notable Features
The distinctive 'ironstone' coloration is the most prominent feature, resulting from the oxidation of the surrounding sediments during fossilization.