Basalt or granite ballast, coarse gravel or crushed stone used for laying the subgrade of highways or railways, primarily for railway subgrades. It is commonly used in the railway transportation system as ballast beneath the sleepers, forming a typical track bed structure. Before laying the tracks, the subgrade is first covered with ballast, compacted, and then sleepers and tracks are installed. The use of basalt or granite ballast facilitates drainage and easy adjustment of track position. Moreover, as the ballast distributes the weight of trains and tracks over the subgrade, it reduces vibrations and noise caused by train passage, enhancing passenger comfort.

And both basalt or granite ballast can dissipate the vibrations and high heat generated by trains passing, maintain the gauge of the rails unchanged, prevent derailment accidents, and reduce noise. Additionally, the gaps between the stones can quickly drain rainwater. Moreover, the ballast made of basalt or granite has strong permeability, which can prevent weeds from growing on the tracks.