Basalt is mostly made up of minerals and has a low resistance to weathering. As a result, basalt as a whole disintegrates faster than granite and other felsic rock types. Magnetite is a prevalent mineral in basalt and makes up the majority of heavy mineral sands. The magnetic property of magnetite causes these materials to be useful in various applications such as building material, filler in paint, and fuel. However, small particles of pure basalt can be used in concrete because its chemical composition is similar to that of limestone. This means that calcium carbonate will precipitate out of solution to form a solid surface layer that protects the inner portion of the concrete. Pure basalt is very hard but does not fracture into sharp pieces like glass. Instead, it tends to crumble into smaller and smaller pieces until it is completely powdery. Over time, this repeated fracturing and re-formation of the surface layer of basalt leads to an erosion of the particle's outer shell which exposes new interior surfaces for further breakdown. Thus, basalt will eventually form a loose, sand-like material under proper conditions. In addition, certain species of bacteria are able to break down the magnetite in magnetite ore bodies using oxygen from water molecules to do so. The by-product of this process is called "biogenic silica" or "siliceous sediment".