Hydroponic systems use various types of rocks including rockwool (Basalt rock), perlite (volcanic rock), diamtomite (sedimentary rock) and clay pellets (shale rock) in place of soil for a growing medium.
About this Author
Diane Dilov-Schultheis has been writing professionally since 2000. She is a food and travel writer who also specializes in gaming, satellites, RV repair, gardening, finances and electronics. She is a member of the Society of Professional Journalists and has been published online at the Travel Channel and Intel.