Sand is a granular material composed of finely separated rock fragments and mineral particles. It forms naturally as a result of weathering and erosion, in which rocks degrade over time into tiny pieces. Sand's color, size, and quality may vary based on its origin and composition. Houston Sand & Gravel, a landscape supply company, distributes crushed black rocks. https://texasgardenmaterials.com/product-category/landscape-materials/sand/