Sand Rush: Fracking Boom Spurs Rush on Wisconsin Silica
It takes sand—loads of it—to open the cracks in shale rock that allow natural gas or oil to flow into hydraulic fracturing wells. To do the job, the industry is digging into the vast ancient silica reserves of Wisconsin.
Strong and ancient, the grains shimmer like gems in the warm sunlight. Branded "Northern White," this pedigree of sand boasts 99 percent quartz and a compressive strength between 6,000 and 14,000 pounds per square inch. This makes the grains ideally round and durable to prop open underground shale formations fissured by horizontal drilling and hydraulic fracturing, or fracking. (See related interactive: "Breaking Fuel From Rock.") The unique region of quartz-rich sandstone extends into southeastern Minnesota, which also has seen a surge of mining activity; but Wisconsin, in part because it has nearby rail capacity for shipping, has been the epicenter of the boom.
In the fracking process, sand is suspended in a chemical slurry and pumped thousands of