sedimentary
Fossiliferous Chert or Limestone
Sedimentary rock containing fossilized marine invertebrates (likely crinoid stems or bryozoans)
Hardness: 7 (if chert) or 3 (if limestone) on the Mohs scale, Color: Dark grey to brown, Luster: Dull to vitreous, Crystal structure: Microcrystalline quartz or calcite
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Physical properties
Hardness: 7 (if chert) or 3 (if limestone) on the Mohs scale, Color: Dark grey to brown, Luster: Dull to vitreous, Crystal structure: Microcrystalline quartz or calcite
Formation & geological history
Formed in ancient marine environments where the remains of calcareous or siliceous organisms accumulated in sediment, compacted, and lithified over millions of years during the Paleozoic or Mesozoic eras.
Uses & applications
Educational specimen, fossil collecting, lapidary display, and geological study of ancient marine ecosystems.
Geological facts
The distinct zigzag or wheel-like impressions visible on the specimen are cross-sections or segments of ancient fossilized organisms, very commonly crinoid stem ossicles (often called 'Indian beads' or 'stone lilies').
Field identification & locations
Found in sedimentary rock formations worldwide, particularly in areas with ancient limestone beds or river gravel bars where resistant chert nodules have eroded out.
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