1. Inert particles such as sand, gravel, crushed stone, or expanded materials, in a concrete, plaster, or terrazzo mixture. 2. Granular material, such as sand, gravel, crushed stone, and iron blast-furnace slag, used with a cementing medium to form a hydraulic-cement, concrete or mortar. 3. Crushed stone, crushed slag, or water-worn gravel used for surfacing a built-up roof. 4. Any granular mineral material.