Mound of Gravel pieces

The Gravel is rock that is of a particular particle size range. Specifically, it is any loose rock that is bigger than two millimeters (2mm) in its largest measurement (about 1/12 of an inch) and no more than 64 millimeters (about 2.5 inches). The next smaller size class in geology is sand, which is >0.0625 mm to 2 mm in size. The next larger size is cobble, which is >64 millimeters to 256 millimeters (about 2.5 to 10 inches). Gravel can be sub-categorized into granule (>2-4 mm) and pebble (>4-64 mm). One cubic foot (28.32 dm3) of gravel usually weighs about 100 pounds (45 kg).

Gravel is an important commercial product, with a number of applications. Many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or tarmac; Russia alone has over 400,000 km of gravel-surfaced roads. Both sand and small gravel are also important for the produce of concrete.