sedimentary
Limestone (specifically Dolomitic/Crystalline Limestone)
Sedimentary Carbonate Rock (CaCO3 / CaMg(CO3)2)
Hardness: 3-4 (Mohs scale); Color: Gray to off-white with yellowish iron staining; Luster: Dull to earthy; Structure: Microcrystalline to clastic texture; Cleavage: Not often visible in rock form, can be rhombic in pure crystals; Specific Gravity: 2.5-2.7
- Hardness
- 3-4 (Mohs scale)
- Color
- Gray to off-white with yellowish iron staining
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (Mohs scale); Color: Gray to off-white with yellowish iron staining; Luster: Dull to earthy; Structure: Microcrystalline to clastic texture; Cleavage: Not often visible in rock form, can be rhombic in pure crystals; Specific Gravity: 2.5-2.7
Formation & geological history
Formed primarily through the accumulation of shell, coral, algal, and fecal debris in warm, shallow marine waters. Over millions of years, lithification turns these sediments into rock. This specimen appears heavily weathered and fractured, typical of outcrop exposure.
Uses & applications
Used widely in construction as decorative stone, cement manufacture, road base, and in agriculture as 'aglime' to neutralize soil acidity.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks. It is the primary source of carbon for carbon dioxide in the atmosphere and is the host rock for many of the world's most famous cave systems.
Field identification & locations
Identify in the field using the 'fizz test'—it will effervesce (bubble) when exposed to a drop of dilute hydrochloric acid (or strong vinegar). Look for blocky fracturing and surface pitting (karst-like weathering). Common in large sedimentary basins globally.
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