Sand is a naturally-occurring granular material comprised of finely divided rock and mineral particles.
Burning noranium could be extinguished with sand. (TNG: "The Vengeance Factor")
The microbrain, an inorganic yet sentient lifeform discovered in 2364, lived in an area it referred to as "wet sand" – a soil layer near the water table of the planet Velara III. (TNG: "Home Soil")
Sand can be used in art to make sculptures. In 2377, Q claimed that the Continuum had "crumbled like a Gelbian sand sculpture" when he threatened to leave them unless they restored his son's powers. (VOY: "Q2")
Crossing a line of sand in a sumo match disqualifies a wrestler. According to Chakotay and Tuvok, Takashi lost the 77th Emperor's Cup because his knee broke the sand, though Kathryn Janeway remembered differently, stating that Takashi won that contest. (VOY: "Latent Image")