Inorganic Materials In Soil. The inorganic materials found in soils account for about half of the total mass of most soil. These inorganic materials take the form of sand, silt and clay, and are referred to commonly as dirt. They form as rocks are eroded by the forces of weather, both wind and rain. Much of the sand and silt is small but visible grains of rock. However, some of it can become so fine that it is microscopic, especially when it comes to clay. Clay is an extremely important part of soil. Because of its porous nature, water is able to seep through clay with ease.