 The dropped salt is eventually washed away and lost, so it may not be reused or collected after gritting runs.By contrast, the insoluble sand can be collected and recycled by street sweeping vehicles and mixed with new salt crystals to be reused in later batches of grit.Sea salt may not be used, as it is too fine and dissolves too quickly, so all salt used in gritting comes from salt mines, a non-renewable source.