Coal gangue
Coal gangue is a different type of stone. It is a by-product of the coal mining process and is made up of shale, siltstone, sandstone and other minerals. Coal gangue has a wide range of applications, including building materials, road construction, and industrial fuel. In addition, it can be used in agriculture as fertilizers, soil conditioners, and even as a replacement for charcoal. The most common use is as an aggregate in concrete and asphalt to improve the durability and strength of these structures.