sedimentary
Limestone with Calcite Veining
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Dark grey to charcoal matrix with white veins; Luster: Dull to sub-vitreous; Structure: Fine-grained (micritic) with crystalline vein infill; Cleavage: Perfect rhombohedral in calcite veins.
- Hardness
- 3 on Mohs scale
- Color
- Dark grey to charcoal matrix with white veins
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 3 on Mohs scale; Color: Dark grey to charcoal matrix with white veins; Luster: Dull to sub-vitreous; Structure: Fine-grained (micritic) with crystalline vein infill; Cleavage: Perfect rhombohedral in calcite veins.
Formation & geological history
Formed in marine environments through the accumulation of skeletal fragments of marine organisms and chemical precipitation. The white veins are secondary calcite that filled fractures in the rock during tectonic stress or groundwater movement.
Uses & applications
Used extensively in the construction industry as aggregate, for making cement, and as a building stone. In ground form, it is used as a soil conditioner in agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. The veins seen in this specimen are often referred to as 'spar' by miners and geologists.
Field identification & locations
Identified in the field by its dark color, fine grain, and positive reaction (fizzing) when exposed to dilute hydrochloric acid. Commonly found in karst landscapes and ancient seabeds. Look for the distinct white crystalline fracture fills.
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