sedimentary

Limestone with Bitumen/Chert

Calcite (CaCO3) containing organic hydrocarbons

AI-generated identification · may be incorrect

Hardness: 3 (Mohs scale) for the matrix; Color: Tan to pale brown with black inclusions; Luster: Dull to earthy; Crystal Structure: Trigonal/rhombohedral calcite; Cleavage: Perfect rhombohedral in calcite crystals.

Hardness: 3 (Mohs scale) for the matrix
Color: Tan to pale brown with black inclusions
Luster: Dull to earthy

Identified May 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in warm, shallow marine environments from the accumulation of shell, coral, and algal debris. The dark spots likely represent trapped organic matter or bitumen that matured under heat and pressure.

Uses & applications

Limestone is used extensively in construction (aggregate, cement) and agriculture. Bituminous limestone can be a source of hydrocarbons or used as an ornamental stone.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. When it contains organic bitumen, it can sometimes emit a faint oily odor when freshly broken or heated.

Field identification & locations

Identify in the field by its softness (scratches with a copper penny) and its effervescence (bubbling) when in contact with dilute hydrochloric acid. Commonly found in karst landscapes and coastal cliffs.