sedimentary
Fossiliferous Sandstone (with Brachiopod or Bivalve mold)
Clastic Sedimentary Rock with Macrofossil Mold
Hardness: 6-7 (sand particles); Color: Tan, beige, or light brown; Luster: Dull/Earthy; Crystal Structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 (sand particles)
- Color
- Tan, beige, or light brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (sand particles); Color: Tan, beige, or light brown; Luster: Dull/Earthy; Crystal Structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and cementation of mineral grains (mostly quartz) and shell fragments in a marine or coastal environment. The fossil impressions were likely created during the Paleozoic or Mesozoic eras when the shell was buried in sediment and subsequently dissolved, leaving a mold.
Uses & applications
Used in construction, as decorative stone, for geological education, and by amateur fossil collectors.
Geological facts
The distinctive ridges on the surface of the rock are 'molds' of an ancient shell. Sandstone covers roughly 20-25% of the Earth's sedimentary rock total. This specific specimen shows 'impressions' rather than the original biological material, which is a common form of fossilization.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and visible layering or fossil imprints. Commonly found in ancient riverbeds, coastal cliffs, and desert environments. Look for symmetry in the fossil patterns to distinguish them from random weathering.
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