sedimentary
Limestone (with potential fossil inclusions)
Calcium Carbonate (CaCO3)
Hardness: 3-4 (Mohs scale); Color: light gray to tan; Luster: dull/earthy; Texture: fine-grained (micritic) to clastic; Cleavage: none; Reacts vigorously with dilute hydrochloric acid.
- Hardness
- 3-4 (Mohs scale)
- Color
- light gray to tan
- Luster
- dull/earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: light gray to tan; Luster: dull/earthy; Texture: fine-grained (micritic) to clastic; Cleavage: none; Reacts vigorously with dilute hydrochloric acid.
Formation & geological history
Formed in warm, shallow marine environments from the accumulation of shell, coral, algal, and fecal debris. This specimen appears to contain small circular pits consistent with marine fossils or ooids.
Uses & applications
Primary source of lime for cement; used in road base, construction aggregate, and as a soil conditioner in agriculture. Small fossiliferous pieces are popular in educational collections.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary host rock for many cave systems due to its high solubility in acidic groundwater.
Field identification & locations
Identify in the field by its softness (can be scratched by a steel nail) and the acid test. Commonly found in areas that were formerly ancient seabeds; check for small depressions that may be crinoid stem or shell fragments.
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