A suspension is tiny (often too small to see) particles in a liquid. It is a mixture. If the particles are relatively large, they will fall out of a solution in time and settle to the bottom as a layer. That is called a sediment. If you mix out soil in water it will make a suspension. The sand will settle out quickly. Silt will settle out over a few hours, but the clay may take many weeks to settle out because it is so small and so close to water in its weight (density).