I was confused about the differences between frac sand and foundry sand, so I asked Jim Drost, a mining and metallurgy engineer from Stillwater, Minn.
His master’s research was on industrial sand and he worked for the U.S. Bureau of Mines on the Reserve Mining case in Silver Bay, Minn., which had many of the same issues.
He told me don’t confuse gravel pits with frac sand. What is mined from an alluvial bed for road use, etc. is called an aggregate.
Industrial sand is high purity silica sand mined from sandstone. This sandstone varies in particle size and is used for glass, sand blasting, foundry, sand paper and fracking.
He said, “It’s all dangerous SiO2.”
Once silica sand is dug or blasted loose, it is washed, dried and screened into different grain sizes and used as described above.
In 2005 developments in drilling techniques and the “Halliburton Loophole” expanded the demand for silica sand, and at premium prices.
The sand market shifted focus thus putting pressure on the price of foundry sand.
In a way, we could look at it as foundry sand being a waste product of frac sand mining and not worth the trouble profit-wise.
Unlike aggregate sand from sand pits, when the silica sand is broken loose by digging or blasting the result is the release of microscopic particles from the “glue” that held the sand together in ridges, hills and bluffs.
Unlike the actual grains of sand, the “glue” is, essentially, shards of glass small enough to be inhaled and small enough to be breathed down to the bottom of the lungs.
Unlike dust from road aggregate and from farm fields which is weathered, the silica sand poses a much greater threat to human health and life.
Jim Drost also said, “Make no mistake foundry sand and frac sand have the same health risks.