sedimentary
Asphalt (Bituminous Slate/Sandstone)
Asphaltum / Bituminous Rock
Hardness: 1-2 (soft); Color: Black to dark gray; Luster: Dull to sub-metallic; Structure: Fragmental/Clastic; Specific Gravity: 1.1–1.5; Cleavage: None
- Hardness
- 1-2 (soft)
- Color
- Black to dark gray
- Luster
- Dull to sub-metallic
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Physical properties
Hardness: 1-2 (soft); Color: Black to dark gray; Luster: Dull to sub-metallic; Structure: Fragmental/Clastic; Specific Gravity: 1.1–1.5; Cleavage: None
Formation & geological history
Formed from the remains of ancient microscopic marine organisms. Over millions of years, heat and pressure transform these remains into liquid bitumen which permeates porous sedimentary rocks like sandstone or limestone.
Uses & applications
Primary source for road paving, roofing shingles, and waterproofing materials. Historically used for mummification and as an adhesive.
Geological facts
Natural asphalt pits, like the La Brea Tar Pits, act as historical preserves, trapping and fossilizing animals from the Pleistocene epoch.
Field identification & locations
Identified by its dark color, faint smell of oil (especially when heated or broken), and slightly tacky or brittle texture. Common in basins with petroleum deposits.
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