Gravel is more or less just like pebbles. Many people find it hard to differentiate between the two. The difference is pebbles are more attractive, well rounded, polished and with good colors whereas gravel is rather dull and irregular in shape.
Pebbles are round semi-polished pieces of rock made smooth by the continuous action of water on them. They are usually obtained near river or sea deposits and comprise of very hard pieces of quartz, chert, silica, and other minerals. Pebbles are pieces of rocks that are at least 5mm in size. Any rock smaller than this is called a ‘grit’