Asphalt

Color: Dark grey to black. Luster: Dull. Hardness: Varies greatly depending on temperature and aggregate. Crystal structure: Amorphous (binders), granular (aggregates).

Asphalt concrete is a composite material made from asphalt (bitumen) and mineral aggregate. The aggregate is typically sand, gravel, and crushed rock. The asphalt acts as a binder. It is an engineered material, not naturally formed in this state. The component materials (bitumen, sand, gravel) are naturally occurring; bitumen is a petroleum product formed over millions of years from organic matter. The laying and compaction of asphalt is a relatively modern geological process, dating back to the late 19th and early 20th centuries.

Primarily used as a paving material for roads, parking lots, airports, and other surfaces. Also used for roofing and sealing.

The term 'asphalt' can refer to both the crude binder (bitumen) and the finished road surface (asphalt concrete). It is the most recycled material in the United States, with over 80% of reclaimed asphalt pavement being reused. Natural asphalt lakes exist, such as the Pitch Lake in Trinidad and Tobago, which is the largest natural deposit of asphalt in the world.

Identify in the field by its dark, granular appearance, typically forming a smooth, durable surface. Often shows signs of wear, cracks, or patching. Commonly found worldwide as the dominant material for road construction. Not a collector's item in the traditional mineral sense, but its composition and engineering properties are geologically significant.