silica gel is a granular, vitreous, porous form of silicon dioxide made synthetically from sodium silicate. silica gel is tough and hard; it is more solid than common household gels like gelatin or agar. it is a naturally occurring mineral that is purified and processed into either granular or beaded form. as a desiccant, it has an average pore size of 2.4 nanometers and has a strong affinity for water molecules.