Silica Sand for Gas Fire Pits and Fireplaces 10 Pounds of Fireproof and Heatproof Base Layer Sand for use Under Gas Logs, Lava Rock or Fire Glass. ... Pure Silica Sand, Medium (70 mesh) for Foundry and Other, kilnDried (10LB) out of 5 stars 1. 23. 99. Get it as soon as Thu, Jun 27.