Heavy soil is a soil with high clay content, which is hard to work with and difficult to cultivate. The solid materials that make up soils are divided into sand, silt and clay. These three groups of substances are mainly determined by the size of their individual particles: sand grains form the largest components with 63 microns to 2 millimeters; silt particles measure 2 to 50 microns; the smallest are the clay particles with diameters below two microns. Larger components (gravel and boulders) are not considered part of the soil type. Soil components that measure more than two millimeters are collectively referred to as the ground skeleton. Depending on which of the three substances prevails, one speaks of sand, silt or clay. If all three components are in roughly the same proportion, this is referred to as clay. The soil type can be used to make statements about some of the essential properties of the soil, such as how it is able to absorb and transfer water or nutrients. The possible uses of a soil are also determined by the type of soil. For example, the ground must have a high clay content to build a dam. In addition, the question of which plants thrive well in a soil depends largely on the soil type.