sedimentary
Limestone (with Iron-Oxide staining)
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3 (Mohs scale); Color: Grayish-white with yellow-brown iron oxide; Luster: Dull/Earthy; Crystal Structure: Rhombohedral (microcrystalline); Cleavage: Perfect in three directions (not visible in massive form); Specific Gravity: 2.71
- Hardness
- 3 (Mohs scale)
- Color
- Grayish-white with yellow-brown iron oxide
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Grayish-white with yellow-brown iron oxide; Luster: Dull/Earthy; Crystal Structure: Rhombohedral (microcrystalline); Cleavage: Perfect in three directions (not visible in massive form); Specific Gravity: 2.71
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. Can also form by precipitation of calcium carbonate from lake or ocean water. Geological age can range from Precambrian to Holocene.
Uses & applications
Primary source of lime for cement, used as an aggregate in construction/road base, soil conditioner in agriculture, and a precursor for glass making.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary rock found in cavern systems and karst topography because it is easily dissolved by slightly acidic groundwater.
Field identification & locations
Identify in the field by applying a drop of cold 10% hydrochloric acid; it will vigorously effervesce (fizz). Found globally in sedimentary basins. Collectors often look for fossil inclusions within the matrix.
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