Gravel is formed of rocks that are unconnected to each other. While common perception of gravel is smaller rocks anywhere between one and three inches around, official designation of gravel includes any rock structures that are not connected to other rocks, even enormous boulders (Wikipedia). Gravel is found naturally, mostly in lake, river, and ocean beds, where the constant movement of the water and waves keeps the gravel from settling and fusing with other rocks; sand is a form of micro-gravel, being tiny stones worn down by constant motion. There are also gravel deposits on dry river and lake sites, which are usually covered by layers of silt and dirt.
Gravel deposits are mined and sifted to create commercial gravel products, which are used in many industrial applications as well as construction. Where natural gravel is scarce, solid stone deposits and bedrock are mined and broken up by machines. Gravel is commonly used to lay beds for roads and foundations; loose gravel is often used on pathways and ornamental gardens. Smaller stones as well as lower-quality stones are often used in cement and blacktop applications, as it adds strength while being relatively cheap. Because of its many uses, gravel remains an important part of industry, and the United States is the leading producer of gravel worldwide.