sedimentary
Limestone with Fossil Fish Fragment
Calcite (CaCO3) containing a fossil teleost
AI-generated identification · may be incorrectHardness 3 (Mohs). Typically light gray to tan, dull to earthy luster. Granular or microcrystalline structure. Reacts vigorously with dilute hydrochloric acid.
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Physical properties
Hardness 3 (Mohs). Typically light gray to tan, dull to earthy luster. Granular or microcrystalline structure. Reacts vigorously with dilute hydrochloric acid.
Formation & geological history
Formed in ancient marine or lacustrine environments via accumulation of calcareous shells, coral, algal, and fecal debris. Fossils indicate preservation in anoxic bottom waters.
Uses & applications
Limestone is primarily used in cement manufacturing, as crushed stone for road base, and as an architectural building material. Fossil-bearing pieces are collected and sold.
Geological facts
The Green River Formation in Wyoming is world-famous for exceptionally preserved Eocene fish fossils in limestone (split into slabs).
Field identification & locations
Identify by relatively low hardness (can be scratched by a coin or knife) and effervescence with weak acid. Commonly found in sedimentary basins worldwide.
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