This is the best type of ballast as it possesses all the characteristics of good ballast. It holds the track to correct alignment and gradient due to its high interlocking action. The stones which are non-porous, hard and do not flake on breaking should be used. Igneous rocks such as granite, quartzite, and trap make excellent ballast. This type of ballast is used for high-speed tracks.
- It is hard and resists crushing under heavy loads.
- It has angular and rough surface and hence gives more stability to the sleepers.
- Its drainage property is excellent.