20/40 SILICA PROPPANT is produced from a very high quality Ordovician St Peter Sandstone layer in our Clayton IA. Quarry. Our line of silica proppants is made of a high-purity quartz sand that is very durable and very round. Our SILICA PROPPANT is highly crush-resistant, and is produced for use by the oil & gas petroleum industry. Pattison SILICA PROPPANT is used in safe and proven hydraulic stimulation processes used for over 70 years on in excess of 2 million oil and natural gas wells. Because shale plays hold vast amounts of oil and natural gas lack adequate pore space for these fluids to flow to a well, our proppants are effective in assisting to hold tiny cracks in the shale open so that these liquids and gases can flow to the well head.