sedimentary
Fossiliferous Limestone
Calcium Carbonate (CaCO3) with Bioclastic inclusions
Hardness: 3 (Mohs scale); Color: Cream, tan, or light gray; Luster: Dull to earthy; Texture: Fine-grained matrix with visible shell fragments and molds; Cleavage: None (rhombohedral in calcite crystals)
- Hardness
- 3 (Mohs scale)
- Color
- Cream, tan, or light gray
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Cream, tan, or light gray; Luster: Dull to earthy; Texture: Fine-grained matrix with visible shell fragments and molds; Cleavage: None (rhombohedral in calcite crystals)
Formation & geological history
Formed in warm, shallow marine environments through the accumulation of calcium carbonate and the remains of marine organisms (shells, corals). The presence of diverse fossils suggests a productive ancient shelf environment, possibly from the Cretaceous or Tertiary periods given the local geology of coastal Angola.
Uses & applications
Commonly used as a building stone, in the production of cement, Lime (calcium oxide), and as a soil conditioner in agriculture. Collectors value it for embedded paleontological specimens.
Geological facts
This specimen contains visible 'steinkerns' (internal molds) and shell imprints. The coordinates provided place this in a region of Angola known for its extensive sedimentary basins that record the opening of the South Atlantic Ocean.
Field identification & locations
Identify by its reaction (fizzing) with diluted hydrochloric acid. Look for visible shell fragments or fossils within the matrix. It is extremely common in the Cuanza Basin of Angola. The local geology aligns perfectly with this sedimentary identification.
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