User blog comment:Katie Liv Phars/Decay: The Theoretical Breakdown of Shigaraki Tomura's Quirk/@comment-35975040-20180713094616/@comment-34934284-20180713095158

True. But sand is made up of small pieces of rocks and other materials, meaning that even if there is a lot of sand, Shigaraki can't touch it with all five fingers. Each grain of sand is too small for that.