sedimentary
Fossiliferous Limestone (containing Brachiopods)
Biogenic Limestone (Calcium Carbonate, CaCO3)
Hardness: 3 (Mohs scale); Color: Tan, beige, or gray; Luster: Dull/earthy matrix; Structure: Fragmental/clastic with visible shell impressions; Cleavage: None (rhombohedral in pure calcite crystals); Specific Gravity: 2.5–2.7
- Hardness
- 3 (Mohs scale)
- Color
- Tan, beige, or gray
- Luster
- Dull/earthy matrix
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Physical properties
Hardness: 3 (Mohs scale); Color: Tan, beige, or gray; Luster: Dull/earthy matrix; Structure: Fragmental/clastic with visible shell impressions; Cleavage: None (rhombohedral in pure calcite crystals); Specific Gravity: 2.5–2.7
Formation & geological history
Formed in shallow, calm marine environments from the accumulation of organic debris such as shell fragments and calcium carbonate precipitates. This specimen likely dates from the Paleozoic era (approx. 250-500 million years ago) based on the brachiopod morphology.
Uses & applications
Used in the production of cement and lime, as crushed stone for road construction, as a soil conditioner in agriculture, and as decorative stone for landscaping or education.
Geological facts
The shell-like patterns are Brachiopods, which are marine animals that look like clams but are biologically distinct. Unlike bivalves, brachiopod shells are symmetrical across the valve rather than between valves.
Field identification & locations
Identify in the field by looking for a 'shell hash' texture and testing with diluted hydrochloric acid (it will fizz/effervesce). Fragments are commonly found in road cuts, quarries, and creek beds in regions with ancient seabed history.
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