Asphalt (Bituminous Slate/Sandstone)

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.

Identified on: 4/22/2026

Mode: Standard