Light grey crushed limestone aggregate. It is typically used as a base for waLimestone screenings are a finely crushed limestone product, sometimes called “chip and dust,” that compacts tightly to create a stable, smooth base for hardscaping projects. They are commonly used as an underlayment for patios, walkways, and driveways, and can also be used to sweep between pavers to lock them in place. lkways, driveways and patios.