sedimentary
Limestone with Calcite Crystals
Calcium Carbonate (CaCO3)
Hardness: 3 on Mohs scale; Color: Gray matrix with white/translucent crystals; Luster: Vitreous to pearly on crystal faces, dull on matrix; Crystal Structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral; Specific Gravity: 2.71
- Hardness
- 3 on Mohs scale
- Color
- Gray matrix with white/translucent crystals
- Luster
- Vitreous to pearly on crystal faces, dull on matrix
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Physical properties
Hardness: 3 on Mohs scale; Color: Gray matrix with white/translucent crystals; Luster: Vitreous to pearly on crystal faces, dull on matrix; Crystal Structure: Trigonal/Hexagonal; Cleavage: Perfect rhombohedral; Specific Gravity: 2.71
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments. The secondary calcite crystals typically form via precipitation from groundwater flowing through fractures or cavities (vugs) within the limestone over millions of years.
Uses & applications
Used in construction as aggregate, in the production of cement and lime, as a soil conditioner in agriculture, and as a decorative building stone. Small crystal specimens are primarily for educational or amateur collecting.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. High-purity limestone is used in the manufacturing of glass and paper. It is also the primary stone used in the construction of the Great Pyramids of Giza.
Field identification & locations
Identify in the field by its strong effervescence (fizzing) when exposed to cold dilute hydrochloric acid or vinegar. Common in karst landscapes and mountain ranges globally. Collectors should look for 'vugs' or hollow pockets where crystals have space to grow.
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