| Beach composed of mixed sand and gravel: In USA, sand is commonly divided into five sub-categories based on size: very fine sand (1/16 - 1/8 mm diameter), fine sand (1/8 mm - 1/4 mm), medium sand (1/4 mm - 1/2 mm), coarse sand (1/2 mm - 1 mm), and very coarse sand (1 mm - 2 mm). Gravel is typically loose rock that is larger than two millimeters (2mm) in its largest dimension (about 1/12 of an inch) and no more than 63 millimeters (about 2.5 inches) |