sedimentary
Asphalt (Aggregate)
Bituminous macadam / Concrete Aggregate
Hardness: 3-5 (varies by aggregate type); Color: Black to dark gray; Luster: Dull to oily/resinous; Crystal structure: Amorphous to microcrystalline; Cleavage: None/unpredictable; Specific gravity: 2.3-2.5
- Hardness
- 3-5 (varies by aggregate type)
- Color
- Black to dark gray
- Luster
- Dull to oily/resinous
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Physical properties
Hardness: 3-5 (varies by aggregate type); Color: Black to dark gray; Luster: Dull to oily/resinous; Crystal structure: Amorphous to microcrystalline; Cleavage: None/unpredictable; Specific gravity: 2.3-2.5
Formation & geological history
Formed through the industrial mixing of crushed sedimentary rocks (like limestone or sandstone) with bitumen, a highly viscous petroleum product. The geological age of the base components ranges from millions of years, though the composite material is relatively modern.
Uses & applications
Primary use in road construction, pavement, roofing shingles, and waterproofing materials. It is the world's most recycled material.
Geological facts
Natural asphalt lakes exist (like La Brea Tar Pits), but most modern asphalt is a byproduct of the oil refining process. It behaves as a non-Newtonian fluid in very high temperatures.
Field identification & locations
Identify in the field by its dark black color, granular texture, and distinctive hydrocarbon odor when heated. It is ubiquitous in urban environments like the street pictured.
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