They main difference is in chemical composition and particle size. Silt is composed of silicate minerals, or those containing silicon and oxygen. Clay is composed of metal silicates, or silicates with metals like magnesium or aluminum associated with it.Clay particles are extremely fine — smaller than 0.002 mm. Sand particles are 2.00 to 0.05 mm in diameter
Explanation: Basically, the main difference is their size.