sedimentary
Limestone with Iron Inclusions
Calcium Carbonate (CaCO3) with Hematite/Limonite
Hardness: 3 (Mohs scale); Color: White to light grey with rusty brown/red staining; Luster: Dull or earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None/Fragmental; Specific Gravity: 2.3-2.7
- Hardness
- 3 (Mohs scale)
- Color
- White to light grey with rusty brown/red staining
- Luster
- Dull or earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: White to light grey with rusty brown/red staining; Luster: Dull or earthy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None/Fragmental; Specific Gravity: 2.3-2.7
Formation & geological history
Formed primarily from the accumulation of shell, coral, algal, and fecal debris in clear, warm, shallow marine waters. The brown iron inclusions are likely due to secondary oxidation or groundwater mineral precipitation.
Uses & applications
Limestone is used as a construction material, an aggregate for the base of roads, in cement manufacture, and as an industrial source of calcium.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary building block of most karst landscapes and cave systems.
Field identification & locations
Identify in the field by its softness (can be scratched by a copper coin) and its effervescence (bubbling) when a drop of weak acid such as vinegar is applied. The rusty spots help locate mineral-rich water paths.
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