Natural materials are defined as products and physical materials from the natural world. This definition is in contrast to man-made or synthetic materials. There is a wide variety of natural materials that exist, and they can be roughly grouped into two categories: organic natural materials and inorganic natural materials.
Organic materials include animal and plant products; materials like wood, fiber, bark and soil are some examples. Inorganic materials are mineral products like stone, metal and composites like clay. Generally, inorganic materials contain traces of organic materials, and vice versa. Inorganic natural materials are, by definition, unprocessed. Sand, for example, is an inorganic natural material composed of silica and other minerals; glass is a processed synthetic product of silica and other additives. Leather, on the other hand, is a processed material from a natural source. Animal skins are not considered immediately natural, as human intervention is required to process the skins to create leather.
Natural materials are considered by some to be a good source of objects for children's play. Stones, pine cones, leaves, nuts and branches are some of the many materials that can be used. Children can benefit from the outdoor setting in gathering these materials and can use them in counting, pointing, building and sorting exercises.