Cobble is a big piece of stone whereas clay is the smallest particles of earth.
Explanation:
Cobble is a small round stone used to cover road surfaces. Pebbles are the round rock fragment with a diameter of 4-64 mm which is smaller than a cobble but larger than a granule. Sand is a loose granular material that produces from the disintegration of rocks, the particles of sand is smaller than gravel. Its particle size is 0.0625 to 2 millimeters. Silt is granular material having a size between sand and clay about 0.002 to 0.05 mm. Clay is a stiff, sticky fine-grained particles that can be molded when present in wet condition and is used to make bricks, pottery, and ceramics. Clay particles are smaller than 0.002 mm in diameter.
