The cover sands in the Republic of Botswana are of four major types: (a) Type 1 is a pure quartz sand found in the northwestern corner of the country. It is derived from a series of ancient longitudinal dunes. (b) Type 2 sand is composed of two major components: probable eolian material with a dominant size around 2.5 o, and a feldspar rich component, largely around 3.0 o in size, that derives from the arkosic Ghanzi Sandstone. (c) Sand type 3 is a pure quartz sand which is statistically similar to sand type 2, but lacks the characteristic feldspathic component. It is assumed that this sand evolved from the breakdown of underlying Karroo Supergroup Sandstones. (d) Type 4 is a fluvially deposited sand found in the eastern part of the country where bedrock outcrop is common and the cover sand thickness is less. There are several sub-varieties of this sand type, each defined by the dominant bedrock source in the area of occurrence. Where the fine-grained "Kalahari" sands (types 1, 2, and 3) lie thickly there is little chance for recharge of underground water supplies, a fact of critical importance in the vast arid areas of Botswana.