Placer material is a type of ORE that is found in stream beds or other bodies of water. It is composed of minerals that have been eroded from rocks and concentrated by the action of water. ORE is a rock or mineral that contains a valuable substance, such as gold, silver, or copper, which can be mined for profit. Ores are usually extracted through mining operations. Ores can also be found in alluvial deposits, which are concentrations of valuable minerals that have been eroded from rocks and concentrated by the action of water.