... A granular material is a conglomeration of discrete solid, macroscopic particles, which can move independently. Some examples of granular materials are coal, sand, rice, coffee, powders. Granular materials do not constitute a single phase of matter but have characteristics reminiscent of solids, liquids, or gases depending on the average energy per grain. If the average distance between granular particles exceeds their dimensions, such system is called granular gas. ...