Driving through America’s heartland leaves no question where all the corn that fattens our livestock, sweetens our food and fuels our cars comes from. Once you venture farther west, you begin to see how other energy needs are met. Endless trains with coal cars snake across the land, plumes from refinery chimneys rise into the sky and oil pumps bob like birds sipping at a pond. It wasn’t until I saw a sign for “Pumice Mine Road” near Mammoth Lakes, California, that I began to think about lesser-known products that come from the earth. Back in the recesses of my mind was the knowledge that the little grey mouse-shaped stone I used to scrub garden dirt from my hands and feet was volcanic in origin, but I never thought of pumice as coming from a mine in the U.S. 

Mammoth Mountain, on the edge of Yosemite, is lined with ski trails, its base home to an upscale ski area. The mountain was formed by a volcano that was active as recently as 50,000 years ago. Among the resultant cinder cones, craters, obsidian domes and lava flows, Native Paiute Indians found materials for their tools and arrowheads, gold miners briefly created a Wild West town, and pumice was mined for a variety of uses. In other areas of California, New Mexico and Oregon, pumice mines are still operating. They grind out the textured rock that formed when molten rock combined with water and air underground and erupted as frothy liquid from vents in the earth’s surface. This hot, frothy rock, once solidified, became hard, airy pumice stones. You’re probably most familiar with the chunky stones used for hand and foot scrubbing, but ground pumice is used in concrete blocks to make them lighter and in creating stone-washed denim, pencil erasers, and even humble cat litter. Gardeners’ hand soaps contain fine pumice, and pumice powder is widely used in teeth-cleaning products as well as in many cleaning products, such as polishes and cleansers. 

Thinking and reading about pumice started me reflecting on other extraction industries we’d passed along I-80. Driving through the moonscape that is the Great Salt Lake, we’d seen huge piles of glittering white material that we assumed was some form of salt being loaded into trucks. Could this possibly be a source of table salt? It turns out that salt from Great Salt Lake is used in the home, but not as a seasoning; food-grade salt would require further costly processing to ensure its purity. Instead, the solar evaporation ponds at the edges of the lake produce salts and brine from which minerals extracted include the sodium chloride used in water softeners, in salt lick blocks for livestock, and to melt ice on road surfaces. Potassium sulfate, used as a commercial fertilizer, and magnesium-chloride brine, used in the production of magnesium metal, chlorine gas, and as a dust suppressant, are also extracted. A magnesium plant on the southwest shore of the lake produces 14 percent of the worldwide supply of magnesium. Magnesium can be mixed with other metals, particularly aluminum, to make car bodies, drink cans and other items that need to be light and strong, so car and appliance manufacturers increasingly using magnesium in their products. Because magnesium is so flammable, one of its main uses is for flares and fireworks. This flammability, however, also causes additional danger when a car made from a magnesium alloy is in an accident. Magnesium also finds its way into our homes: milk of magnesia, a compound of magnesium, hydrogen and oxygen molecules, works as a laxative and to treat indigestion. Another home remedy made with magnesium? Epsom salts, otherwise known as magnesium sulfate. The name “Epsom” comes from a spring in England where the salts occur naturally.



Between Utah’s Salt Lake and Mammoth Mountain’s pumice, if you’re traveling along and take a break from reading the road signs announcing the next source of caffeine and diesel fuel, you’ll see vents in the earth with steam rising from them, a sure sign of not just hot, but boiling, springs. Near some of these springs, EP Minerals, in Lovelock, Nevada, mines diatomaceous earth, clay, perlite and cellulose. These industrial minerals, which are defined as non-metallic minerals produced from natural sources, are used as filter aids, absorbents and functional additives in food and beverages, biofuels, swimming pools, oil and gas, products for farm, home and landscape, sports turf, paint, plastics, insecticides and more. In an average day, you probably come in contact with hundreds of items that have been manufactured or processed from industrial minerals. They help filter beer and wine and are an additive in paint. You may have used diatomaceous earth as a slug repellent in your garden. EP Minerals produces a freshwater, food-grade diatomaceous earth insecticide with no added chemicals that is used for grain storage, on animals, and all around a farm, home or garden. Diatomaceous earth powder is part of a thick coating used to make tiny seeds large enough for mechanical planting, or to provide a thin protective coating on larger crop seeds such as soybeans. Diatomaceous earth and calcined clay products are also used as soil amendments, designed to reduce water usage, improve drainage, reduce soil compaction and improve plant health. In addition, it’s used as a granular filter medium to remove arsenic and other contaminants — phosphate, chromium, selenium, fluoride and antimony — as well as lead from drinking water.

Perlite is used in filtration as well, and also in biofuels, construction products, pharmaceuticals and soil amendment products. Granular clay is used in your everyday kitty litter, in environmental remediation, oil spill removal, and in sports field and landscape products. There seems no end to the application of minerals that are found beneath Western soils, their presence hardly ever thought about, but their uses legion.