A Case History - 1990-2000

By Ralph E. Pray, D Sc., Met Eng

The first requirement for a successful mine operation is a market for the product, metallic or nonmetallic. The second requirement is to deliver a quality salable product to that market for payment in an amount exceeding the cost of the operation. There are a vast number of mineral products, literally from A to Z, and there are an infinite number of ways to get them out of the ground and delivered in a form acceptable at the marketplace.

One may start by looking at what a particular industry needs, such as silica for glass or cement manufacture. Low-iron silica is desperately needed for making glass, and at least one California cement company would dearly love to see a prospector walk in the front door with samples from his nearby silica claims.

Another example, also nonmetallic, is bentonite clay, the water impervious material commonly mandated to line the floors, walls, and caps of landfill disposal sites. This material, which swells when wet, is extensively used in oil drilling mud. Bentonite frequently occurs along earthquake faults and it was along the Garlock Fault in Kern County that Joe Mathewson, a Los Angeles area resident, searched for the commodity in the 1980s. He found a suitable deposit on land next to Red Rock Canyon State Park east of Mojave. The swelling-type calcium bentonite clay was tested by independent laboratories and was determined to meet the low permeability specifications for landfill use.

Mathewson purchased the land, which had been actively mined during its pre-WWII years as the source of Old Dutch Cleanser kitchen and bath scrubbing powder. Over 120,000 tons of white, high-quality pumicite had been mined underground. The bentonite occurs as a layer over the pumicite, in places very close to the surface. The exposed edge of the clay overlooks Last Chance Canyon for thousands of feet. The layered beds in this portion of the Ricardo Formation dip twenty degrees northeast and plunge beneath Highway 14 to the north.

Mathewson had the pumicite tested for a variety of uses, such as an abrasive, a filler product, a pesticide carrier, and as a Portland cement additive. Investigations performed at the Mineral Research Laboratory, with the assistance of the Materials Testing Laboratory at California State Polytechnic University at Pomona, showed an increase in concrete strength using pumicite, but at an unacceptable cost.

Applications for a conditional use and operating permit for surface mining were submitted to Kern County and State of California officials in 1988 and after several revisions were approved in 1989. The Kern County Department of Planning and Development Services issued a Conditional Use Permit containing 46 major conditions required before, during, and after operating on the property. For several years truckload shipments of pumicite were sent to an eastern market, but interest was weak. Meanwhile, the owner, determined to avoid capital expenses for equipment, located a contractor who would perform the necessary stripping and reclamation operations as needed, and truck the raw product to a distant mill for fine grinding. Removed overburden had to be carefully spread to conform to the existing topography and ground surface characteristics. In order to meet landfill specifications another contractor was hired to dry, crush, and screen the bentonite on-site using a portable plant.

Mathewson set prices on his calcium bentonite at $35 per ton for pit run, $45 per ton for minus 10-mesh material, and up to $80 per ton for finely ground and screened product, truck-loaded at the mine. Fine material was also super-sacked on-site. His direct costs for minus 4-mesh were about $22 per ton, leaving a profit of $15 per ton. Existing roads were used for all transportation across BLM land to the highway. His overhead costs, with no equipment, labor, insurance, or office help, were minimal. He had minor legal, travel, product research, and permit fee expenses.

Mathewson notified all Southern California landfill contractors and city/county offices involved in landfill administration that his bentonite was accepted and available for landfill sealing against seepage. Twenty-one separate sales contracts were awarded between 1991 and 2000 for a total of 20,000 tons of bentonite. Surface mining and processing at the rate of up to 100 tons per day with large equipment meant that the mine operated for an average of only about 20 days each year for the life of the operation. As sales and mine operations were based solely on demand and landfill activity, there was no production during 1996 and 1997. A listing of the production times and tonnages shows how versatile the operator had to be in order to accommodate his buyers if he wanted to stay in business.

1991  Orange  1.25  $111 
1991  Inyokern  272.08  $22,582 
1991  Inyokern  137.44  $11,000 
1991  Inyokern  26.45  $2,194 
1991  Houston  268.83  $20,969 
1992  Riverside  25.815  $2,168 
1992  Tehachapi  648.51  $43,396 
1992  Moreno Valley  25.815  $2,000 
1993  Santa Fe Springs  1,142.48  $94,825 
1993  Irvine  65.53  $2,924 
1993  Scottsdale  22.5  $2,002 
1994  Carson  796.13  $34,418 
1995  Livermore  500  $32,500 
1995  Irvine  14  $490 
1995  Irvine  1,501.2  $52,542 
1995  Irvine  11,178.54  $569,086 
1995  Irvine  1,427.67  $49,965 
1998  Santa Monica  1,886.3  $160,338 
1999  Terra Bella $805 
2000  Terra Bella   24  $3,840 
2000  Terra Bella  24  $3,840 
  TOTAL  20,000  $1,113,945 

The total tonnage removed in ten years by Mathewson was about the same as that mined in the entire State of California in 1987. Wyoming, by comparison, produced over two million tons of swelling bentonite in 1987. Mathewson's mine operated sporadically for only a few weeks at a time, sometimes for only a day, definitely qualifying it as a small mine. The owner had a full-time job and spent some of his vacation time at the mine. In addition, he networked with officials and contractors in the business he was selling to.

Other small bentonite operations on the same formation, to the west, had taken place as far back as the 1920s. Martin Engel, the old assayer at nearby Cantil, described to the author in 1969 how the wet clay was used for facial cleansing mud by the "ladies of the night" in Mojave during the rip-roaring mining days of the 1930s. In 1970 the Mineral Research Lab mined and chemically modified a shipment of Red Rock Canyon bentonite to produce high-temperature grease for testing by the National Grease Institute. The test was a success but the sales effort lacked Joe Mathewson's drive to get the wheels of progress rolling. Marketing is a big part of any business.

"The second requirement is to deliver a quality salable product to that market for payment in an amount exceeding the cost of the operation." That is pretty much the main guideline for any successful business. The majority of miners hoping to get into business are principally interested in gold. If you intend to become an independent hardrock gold miner you have to have something like two-ounce per ton rock three feet wide these days. That would keep good tires on the pickup and the old lady in party dresses. But there isn't any two-ounce rock to speak of. If the search is healthy and enjoyable away from your daytime job, that may be all you need. If you decide you must have a salable hardrock product or property, to mine or to lease out, the gold business is probably not a good idea.

There is, however, a valuable mineral commodity for just about every letter in the alphabet. And our American West has most of them. The serious hardrock prospector might do well to put gold on the back burner and look at industrial minerals. If you're itching to get out in the boonies and break some rock, think nonmetallic!

If you don't know exactly how to look for it in the field, go anyway. Get started. This prospector went along the Garlock Fault on a rainy Sunday in 1969 looking for bentonite clay without any idea about its appearance, what it looked like in the ground. No one could have been more poorly informed. But I knew it was slippery when wet. Walking down a gray-colored hill in the drizzle I slipped and fell. The long streak of freshly-uncovered bentonite was immediately staked as the Rainy Day claim. This was the source of material for chemical modification to high-temperature grease.

Finally, for this article, a last look at Joe Mathewson, the small mine operator who could and did. Now he's involved with acquiring and permitting a wide variety of minerals, including limestone, dolomite, magnesite, dimension stone, zeolite, diatomaceous earth, iron ore, granite and colored clay, all located on the public domain.

Dr. Ralph Pray, Mining & Metallurgy

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