History of the Silver Bell Mining District

The Arizona Geological Survey has just released another paper about Arizona mining: The History of the Silver Bell Mining District (AZGS Contributed Report CR-17-A). The paper is authored by geologist and mining historian David Briggs who has written about many of Arizona’s mining districts. The paper is available for free download (link).

The Silver Bell mine and the town of Silverbell are located about 36 miles northwest of Tucson, Arizona. It has produced copper and other metals since 1873 and silver since 1865. Prior to that, the Tohono O’odham Indians and/or their predecessors mined turquoise, hematite and clay, which were used for pottery, paint and decorative purposes.

The Silver Bell mine has had a colorful and sometimes contentious history. Briggs writes that “Over the past 150 years, the Silver Bell mining district evolved from a collection of small, intermittent, poorly financed and managed underground mining operations that struggled to make a profit from high-grade ores; to a small but profitable producer, deploying innovative mining practices and advancements in technology to successfully develop the district’s large, low-grade copper resource.”

Besides a detailed history of owners and operations, the report contains many historic photographs of the mining operations and the town.

Briggs: “Over past 130 years, the Silver Bell mining district yielded approximately 2.27 billion pounds of copper, 6.6 million pounds of molybdenum, 3.7 million pounds of lead, 40.8 million pounds of zinc, 2,100 ounces of gold, and 5.95 million ounces of silver.”

The mine now produces copper by leaching and electro-winning. Remaining reserves are reported to be 214.4 million tons, averaging 0.283% copper. Local geologists suspect there are more copper resources east and west of the active mining area, but that ground is effectively off-limits because it lies within Ironwood Forest National Monument. The monument was imposed over valid pre-existing mining claims. IFNM is one being reconsidered by the Trump administration.

Other papers by David Briggs:

History of the Ajo Mining District, Pima County, Arizona

History of the Warren (Bisbee) Mining District

History of the San Manuel-Kalamazoo Mine, Pinal County, Arizona

Recovery of Copper by Solution Mining Techniques

Superior, Arizona – An Old Mining Camp with Many Lives

History of the Copper Mountain (Morenci) Mining District

History of Helvetia-Rosemont Mining District, Pima County, Arizona

History of the Ajo Mining District, Pima County, Arizona by David Briggs

Geologist David Briggs has written another interesting paper on the history of mining in Arizona. This 18-page paper, History of the Ajo Mining District, Pima County, Arizona, was just published by the Arizona Geological Survey and is available as a free download:

I was particularly interesting in the Ajo paper because as a geologist, I conducted exploration at the mine and in the district. Although the mine is now inactive, there is remaining mineralization that can be mined given the right economic conditions. The Ajo orebody is particularly interesting to geologists because paleomagnetic and geologic evidence indicates that the Ajo ore deposit has been tilted to the south a total of approximately 120 degrees in two separate tectonic events. (Source) There is also speculation that a detached piece of the original orebody lies hidden nearby.

Briggs begins his story as follows: “The hostile environment of southwestern Arizona’s low desert presented many challenges to those who sought to discover and exploit the mineral wealth

of the region. Ajo’s remote location combined with hot summer days and scarce water created a number of obstacles that needed to be overcome. Despite these impediments, the district’s wealth was mined by Native Americans long before the arrival of first Spanish explorers, who recognized its potential soon after establishing outposts in this region.”

The Ajo area has a long history. Prior to the arrival of the first Spanish explorers in the 1530’s, the native Tohono O’odham Indians and their ancestors mined hematite, an iron oxide, which they used as body paint. Establishment of Spanish missions in Southern Arizona provided bases from which prospectors combed the country.

With the signing of the Treaty of Guadalupe Hidalgo at the end of the Mexican American War on February 2, 1848, and the subsequent Gadsden Purchase in June 1854, many prospectors tried their luck at Ajo.

Briggs provides great detail as he recounts the many lives of mining ventures in Ajo. Following is a very brief sketch of major events.

The first formal mining began in 1855 and a wagon road was constructed to the railroad at Gila Bend. Ore was also sent by wagon to San Diego and shipped to Swansea, Wales for smelting. High transportation costs eventually made the venture uneconomic.

Briggs recounts the era between 1898 and 1908 when the Ajo deposit saw many promotions and fraudulent mining schemes.

In 1911, the Calumet and Arizona Mining Company, which was operating mines in Bisbee, became interested in the Ajo properties and acquired the New Cornelia Copper Company which owned Ajo at the time. Calumet began an extensive drilling program which confirmed the presence of a large sulfide body of mineralization. They began open pit mining in 1915.

In 1931, Phelps Dodge merged with Calumet and Arizona Mining Company and continued to operate the mine which they did until 1985 when a combination of low copper prices and stricter regulations for smelter air quality caused the company to close the mine.

The Ajo property is now owned by Freeport-McMoRan, Inc. through its merger with Phelps Dodge. According to Briggs, “Freeport continues to periodically assess the economic feasibility of returning the Ajo project to production. As of December 31, 2015, this project is estimated to contain a sulfide resource of 482 million short tons, averaging 0.40% copper, 0.010% molybdenum, 0.002 oz. of gold/ton and 0.023 oz. of silver/ton.”

Other papers by David Briggs, published by the Arizona Geological Survey:

History of the Warren (Bisbee) Mining District

History of the San Manuel-Kalamazoo Mine, Pinal County, Arizona

Recovery of Copper by Solution Mining Techniques

Superior, Arizona – An Old Mining Camp with Many Lives

History of the Copper Mountain (Morenci) Mining District

History of Helvetia-Rosemont Mining District, Pima County, Arizona


History of the Warren Mining District, Bisbee, Arizona

The Arizona Geological Survey has just released a new report “History of the Warren (Bisbee) Mining District” located near the town of Bisbee in Southern Arizona. The author is economic geologist David Briggs. This well-illustrated,10-page report may be downloaded as a free PDF file (7.7Mb):

Lavender pit

Over the life of the Warren mining district (1880-2013), 3,961,479 tons of copper, 162,128 tons of lead, 177,524 tons of zinc, 14,000 tons of manganese, 2,792,000 ounces of gold and 102,215,000 ounces of silver were recovered from the area’s mines. It was Arizona’s seventh largest copper producer, top producer of lead, second largest producer of zinc, fourth largest manganese producer, largest gold producer and second largest silver producer.

Citation: Briggs, D. F., 2015, “History of the Warren (Bisbee) Mining District, Arizona Geological Survey, Contributed Report CR-15-B.

Breccia pipes of northwestern Arizona and their economic significance

Breccia pipes are vertical collapse structures, typically a few tens to hundreds of feet across and hundreds to thousands of feet in vertical extent. The pipes formed more than 200 million years ago within Paleozoic and Triassic rocks over a broad area of the Colorado Plateau around the Grand Canyon. The pipes formed as groundwater, flowing through the Redwall Limestone, dissolved material along fracture zones and created caves. Continued dissolution caused collapse of overlying rocks into the caves forming breccia pipes and sink holes.

Breccia pipe secton

BP hwy 89The Survey has identified “1300 pipes or suspected pipes” in the region. “Mineralized breccia pipes—pipe-like masses of broken rock—may contain high-grade uranium ore and variable amounts of copper, gold, silver, vanadium and other mineral ore. More than 71 mineralized breccia pipes have been discovered in the region, and as of 2010, nine of these pipes yielded more than 10,500 metric tons of uranium.” “It appears from this work that the number of suspected breccia pipes is one to two orders of magnitude greater than previously recognized. (The number may be even higher since many pipes do not yet have a surface expression.) The study raises the possibility that the higher concentration of breccia pipes is likely to extend across the entire region.” This means also that there is potential for much more uranium and other valuable minerals.

The Arizona Geological Survey has just completed and made available a new report “Partial database for breccia pipes and collapse features on the Colorado Plateau, northwestern Arizona” which you can download here. The cover of the report shows Highway 89 crossing a depression, the surface expression of a breccia pipe.

Breccia pipe map NW AZ

The breccia pipes exist because of the nature of the Redwall Limestone, a 350-million-year old formation that forms high red cliffs near the bottom of the Grand Canyon. The limestone is actually grey, but has been stained by iron and manganese oxides derived from overlying formations.

The Arizona Geological Survey has another publication on the history of the Redwall Limestone itself. You can download it here. That publication is non-technical, has many illustrations and is suitable for the layman or classroom.

Among the properties of the Redwall Limestone are:

• Diverse and long history over the last 350 million years.

• Magnificent cliffs and red walls.

• Composed of ~99.5% pure limestone, ~95% of which is biologically formed in the

presence of organisms.

• Forms very chemically-resistant cliffs, yet it is a very soft rock (slightly harder than a

finger nail).

• Has thousands of miles of interconnected caverns spread out over the Colorado Plateau.

• Has many caverns, some with ancient and modern speleothems.

• Is the source of carbonate for the growth of abundant travertine deposits.

• Provides precious minerals, trace metals and uranium in breccia pipes

• Is a major source of high-quality groundwater to numerous and voluminous springs in

the canyon and region, consumed by most visitors to the canyon.

• “Living in the Past” implies the past of the Redwall Limestone is living with us today

Although the area holds great potential for mineral resources which could be mined with minimal disturbance to the environment, radical greens and their Congressional fellow travelers are bent on banning mining in the area.

On January 9, 2012, the Obama administration announced a 20-year ban on new mining claims on public land near Grand Canyon National Park, thereby denying access to valuable minerals resources. Now there is a proposal to establish “Grand Canyon Watershed National Monument” which would cover 1.7 million additional acres (see green areas on the map here). If established, then all mineral potential of the area would be off limits. See details of current and pending areas made off-limits to mineral production here.

See also:

Uranium mining and its potential impact on Colorado River water

Uranium mining ban near Grand Canyon all politics, no science

Arizona was #1 mineral producer in 2014

According to the U.S. Geological Survey’s Mineral Commodity Summary for 2015, Arizona was the top non-fuel mineral producer in the U.S. in 2014, edging out Nevada which fell to number two because of the drop in gold prices. The top 12 States each produced more than $2 billion worth of non-fuel mineral commodities. These States were, in descending order of value: Arizona, Nevada, Minnesota, Texas, Utah, California, Alaska, Florida, Missouri, Michigan, Wyoming, and Colorado. (Delaware comes in last with $14 million worth of sand and gravel, magnesium compounds, stone, and gemstones.)

In 2014, Arizona produced $8.06 billion worth of minerals which represented over 10% of total U.S. production. Major non-fuel minerals were copper, molybdenum concentrates, sand and gravel, cement, and crushed stone. Arizona produces over two-thirds of U.S. domestically mined copper.

The total impact of the mineral industry on the U.S. economy of was $17.4 trillion in 2014. That figure includes mining, processing, and value added by manufacturing.

The USGS notes that the U.S. is at least 50% reliant on imports for consumption of 43 mineral products and is 100% reliant on imports for 19 of those minerals. However, the U.S. was a net exporter of 17 mineral products.

The table below shows mineral industry trends of production, employment, and wages.

Mineral industry trends 2014

The USGS says:

“The estimated value of U.S. metal mine production in 2014 was $31.5 billion, slightly less than that of 2013. Principal contributors to the total value of metal mine production in 2014 were copper (32%), gold (27%), iron ore (16%), molybdenum (10%), and zinc (6%). Changes in average prices for domestically mined metals were mixed in 2014. After increased yearly average prices from 2002–12, gold prices decreased for the second consecutive year. The estimated value of U.S. industrial minerals mine production in 2014 was $46.1 billion, about 7% more than that of 2013. The value of industrial minerals mine production in 2013 was dominated by crushed stone (28%), cement (17%), and construction sand and gravel (15%). In general, industrial minerals prices increased slightly.”

The Mineral Commodity Summary document provides detailed information on 83 mineral commodities.

Importance of Copper to manufacturing and us

Copper is vital to our civilization. It is used in many things we may take for granted. Below is an infographic from the National Mining Association showing how copper is used and where it is mined in the United States (you can get the graphic here).

copper final

You can also get a new report “U.S. Mines to Market” which shows the importance of mining to the manufacturing segment of our economy.

Among other things, the report discusses:

In 2013, value added to gross domestic product (GDP) by major American industries that consume processed mineral materials was $2.4 trillion, or 14 percent of total GDP.

As the U.S. manufacturing sector continues to grow, the importance of a secure, stable, reliable and sustainable raw material supply is increasing.

The U.S. permitting process for new mineral and metal mines makes it difficult for our nation to reduce dependence on foreign-sourced raw materials. As it stands, the average waiting period for U.S. mine permitting is seven to ten years. Just to put that into perspective, in Canada and Australia—countries with similarly stringent environmental regulations—the waiting period is two years.

In regard the that last point, see my posts:

If it can’t be grown, it has to be mined

Minerals vital to modern life

How NEPA crushes productivity

Mining and the bureaucracy

Distinguishing Fact from Fiction about Rosemont

This article is a guest post by David Briggs.  The opinions expressed are his own.


Distinguishing Fact from Fiction

By David F. Briggs

When listening to the statements put forth by leaders of groups opposing the Rosemont Copper project, think about what they are saying. Then ask yourself; does this really make any sense?  Is this logical?  What are their motives for making these statements?

While many valid concerns have been raised by the public, these issues have been addressed during the permitting review process.  Despite this, groups like the Save the Scenic Santa Ritas dispute these findings and continue making arguments that are based on emotion and not supported by the facts or the rule of law.  Other statements contain partial truths designed to support their arguments, which upon closer examination reveal crucial information refuting their position has been conveniently omitted.  Many of their arguments are not even applicable to the point that they are trying to make.

Let’s examine one quote by Ms. Gayle Hartmann, which was made at a Save the Scenic Santa Ritas’ fundraiser held on June 5, 2013 in Green Valley.

“Now turning to Rosemont, what is it?  It’s a wholly-owned subsidiary of Augusta Resource Corporation and Augusta Resource is a Canadian junior based out of Vancouver, Canada.  A Canadian junior is not a pejorative term, it just means that Augusta is not a mining company.  It is a group of individuals, who speculate in mining stock.  And these individuals, that is the board of Augusta, pay themselves very well.  What’s more, Augusta has never run a mine. They have never mined an ounce of anything anywhere.”

Ms. Hartmann’s statement is hardly an accurate characterization of Augusta Resource Corporation or junior mining companies.  First of all, juniors, such as Augusta Resource, are mining companies that primarily rely on equity financing as the principal means of funding their business activities.  Most junior mining companies specialize in exploring and developing mining properties. Like Augusta Resource, they employ professional staffs and highly qualified consultants to conduct activities that ultimately enable them to  supply the minerals society requires to meet its present and future needs.

Although many small mining operations are managed and operated by junior mining companies, others like Augusta Resource are working to develop their first mining operation.  There is no reason why a junior mining company cannot grow into a mid-sized or major mining company.  A local example is the recent acquisition of the long-established Pinto Valley copper mine by the Canadian junior, Capstone Mining Corporation, who will now step into the mid-size company category.

One of the best examples of a junior mining company becoming a major company in the gold mining business is the Barrick Gold Corporation.  Initially founded in 1980, Barrick Petroleum was an unsuccessful, privately owned oil and gas company.  It became a public traded mining company in May 1983, when its name was changed to Barrick Resources Corporation.  Over the next two decades of wise mergers, the purchase of established mining properties and efficient operations, this junior mining company became the world’s largest gold producer.  Similar to what Barrick did with its many acquisitions in Canada, Nevada and overseas, Augusta Resource Corporation has acquired and developed a very promising property that will provide a firm foundation on which to build a profitable business.

Individuals and institutions, who have invested in the Augusta Resource Corporation and committed to finance the Rosemont Copper project, have a very good understanding of the risks involved and the track records of the highly qualified professionals, who manage these companies.  Their confidence in the economic viability of this 21st century mining project and its management is demonstrated by their willingness to participate in this business venture.

The motives behind Ms. Hartmann’s statements made at the Save the Scenic Santa Ritas’ recent fundraiser were self-serving.  However the fact remains, the Rosemont Copper project would have never reached the final stages in the permitting process had it not been for the professional expertise and conduct of the management and staff of Augusta Resource Corporation and its subsidiary, the Rosemont Copper Company.

David F. Briggs is a resident of Pima county and a geologist, who has intermittently worked on the Rosemont Copper project since 2006.  He can be contacted at

Copyrighted by David F. Briggs.  Reprint is permitted provided that credit of authorship is provided and linked back to the source.



Future of Rosemont Mine Very Certain

This article is a guest post by Rick Grinnell, VP, Southern Arizona Business Coalition, in response to a press release from opponents of the Rosemont Mine.

In a recent press release by Save the Scenic Santa Ritas (“Augusta Resource Shareholders Meet, Future of Rosemont Mine Uncertain”) stating the future of Rosemont uncertain, it is apparent that this audience doesn’t understand the business of financing for major development projects or the mining industry’s history of financing. They don’t grasp or refuse to acknowledge standard financing practices of a development of this magnitude. Investors have different objectives and some are willing to take higher risks at the beginning of a project for a higher rate of return, while others may wait until certain  bench marks and goals have been reached. This isn’t the first project for this type of investment and won’t be the last.

This group’s endless attacks have proven to be filled with innuendo, misstatements and in some cases, what I perceive as intentions to slander the integrity of the project and the management team. This team has over 550 years of mining experience and are some of the best in this industry. On a personal note, we here in Southern Arizona are fortunate to have this industry and the quality of personnel as neighbors and citizens. This company will be a genuine partner for many years. The good people of Rosemont Copper are personally invested, serving on various charity boards and organizations.

The opponents of Rosemont have lost every appeal. The facts cannot be discounted by emotional rhetoric and the dissemination of blatant misrepresentations of this mining project. The initial objections  have been answered through an educational process about the Rosemont project. I can confidently state the greater majority of citizens of Southern Arizona are satisfied that Rosemont Copper will bring a desperately needed economic boost to our area and will do so in the most responsible and respectful way possible. This is the next generation of mining.

Finally, I take issue with Mr. Ray Carroll’s (Pima County Supervisor, District 4) assertions that the investors are being misled and, in other public forums, that this project will devastate Southern Arizona. He  continues to attack Rosemont’s integrity without factual substance or merit. His continued sarcastic, arrogant and disrespectful comments are not that of a Statesman, but rather a bully on the prowl to gain personal or political leverage in his quest to find significance in his position.

Despite the continued efforts of the opposition to malign this project, the law, the facts and the integrity of the process will prevail.

The value of mining in Arizona

Without minerals, we would not have electricity, food, or shelter. Minerals make today’s technology-based life possible, but that’s something many of us take for granted. We want the benefits from those minerals, but some want mining of minerals to be in somebody else’s neighborhood.  The importance of mining has long been recognized:

If we remove metals from the service of man, all methods of protecting and sustaining health and more carefully preserving the course of life are done away with.  If there were no metals, men would pass a horrible and wretched existence in the midst of wild beasts…  -Georgius Agricola, in De Re Metallica, 1556.

For Arizona, it is not just metals.  Arizona produces sand and gravel, limestone for cement production, coal for electrical generation, and a variety of industrial minerals which contribute almost $2 billion to Arizona’s economy (see here).

Arizona has a long history of mining.  There is archeological evidence that cinnabar, coal, turquoise, clay, pigments, and other minerals were mined in Arizona beginning at least 3,000 years ago. (See A History of Mining in AZ by the Arizona Mining Association.)

According to the Arizona Mining Association, Arizona currently produces 68% of domestically mined copper.  With that copper production comes by-product molybdenum, gold, silver, platinum, and rhenium.  Incidentally, The Sierrita Mine south of Tucson is currently the onlydomestic producerof rhenium, a metal used in high-temperature, super-alloy turbine blades for jet aircraft and other land-based turbines.  The Sierrita plant processes output from other mines on a toll basis. It may soon be joined by a second rhenium plant at the Kennecott (Rio Tinto) mine in Utah.

The direct and indirect economic impact of copper mining on Arizona’s economy is about $4.6 billion annually.  That includes $3.2 billion in personal income,  $500 million in state and local government revenues, and 49,800 high-paying jobs for Arizonans. Average labor income of mining company employees (including benefits) is $108,000 per worker vs. $47,000 for all Arizona workers.  If we add in non-metallic, non-fuel, minerals, then Arizona produced about $8 billion worth of mineral products in 2012 according to the U.S. Geological Survey.  Arizona ranks second, after Nevada, in value of total mineral production.  The U.S. total value of mineral production was about $76 billion which supported more than 1.2 million jobs in 2012.

Arizona is endowed with great mineral resources as shown on the map below prepared by the Arizona Geological Survey.


Currently ASARCO and Freeport-McMoRan Copper & Gold are the two biggest copper producers in the state.  ASARCO operates three mines and a smelter. According to the Southern Arizona Business Coalition, in 2012 ASARCO paid wages and benefits of $215.8 million, property, severance, and sales taxes of $47.2 million, and employed 2,198 people in Arizona. Freeport operates mines in Safford, Morenci, Bagdad, Miami, and Sierrita.  They paid wages and operational spending of $860 million in 2012, taxes of $274 million while employing 7,600 people directly and indirectly employing an additional 30,000 people.

In addition to past and current mining, there are many projects on the horizon, some in the exploratory stage, others navigating the byzantine regulatory permitting process.  (See my posts: Mining and the bureaucracy and How NEPA crushes productivity)

Perhaps the largest project is that of Resolution Copper near the town of Superior just west of the famed Globe-Miami mining district and just north of ASARCO’s Ray mine.  This is a bold undertaking because the orebody is 7,000 feet below the surface.  Resolution says that at peak production, this mine will be the largest copper mine in North America, producing over one billion pounds of copper per year.  Resolution estimates that over the 64-year life of the mine, the project will generate $61.4 billion in economic value, provide $20 billion in tax revenues, and provide 3,700 permanent jobs.

The Rosemont copper mine south of Tucson is nearing the end of its long journey through the regulatory maze, and mine construction may begin early next year.  This mine will generate 2,900 Arizona jobs and inject $19 billion into Arizona’s economy and pay $404 million in local taxes over its 20-year projected life.  The mine expects to produce 243 million pounds of copper per year.

Curis Resources is developing an in-situ copper mine near Florence, Arizona.  In this project, instead of mining rock, Curis Resources “seeks to dissolve copper minerals from an underground deposit by introducing water with a lowered-pH (making it slightly acidic).This low-PH, water-based solution dissolves the copper and allows it to be pumped to the surface through a continuous loop water treatment system.”  This deposit, lying 400-to 1200 feet below the surface contains approximately 2.84 billion pounds of copper.

Curis estimates that over the projected 28-year life of the project, it will generate $2.2 billion in economic activity for the state of Arizona, $1.1 billion in economic activity for Pinal County, $325 million in taxes and royalties for Arizona government, and $1.46 billion in increased personal income in Arizona, 170 direct jobs at the project site in Florence, and 681 jobs in the state of Arizona.

TheI-10 copper deposit, located along Interstate 10 between Benson and Willcox, Arizona, is being investigated as another in-situ copper leaching project by  Excelsior Mining Corporation, a Canadian junior company. They estimate the deposit currently contains an indicated oxide copper resource of 3.21 billion pounds and an additional inferred oxide copper resource of 0.88 billion pounds.

Wildcat Silver Corporation is in the exploration stage of its Hermosa Project which is evaluating the silver-manganese potential in the historic Hardshell mining district near Patagonia in Southern Arizona. Their preliminary economic assessment estimates a measured and indicated resource of 236 million ounces of silver and an inferred silver resource of an additional 79 million ounces.  Project life is estimated at 16 years.  Wildcat estimates that annual production will be 4.1 million ounces of silver, 233,000 tons of manganese carbonate, 20,187 tons of zinc cathode, and 960 tons of copper.

Copper Creek is an old mining district located on the east bank of the San Pedro River and on the western slope of the Galiuro Mountains about 75 miles northeast of Tucson. The property has been acquired by Redhawk Resources, a Canadian junior mining company that plans to develop an underground mine for copper, molybdenum, and silver.  Redhawk estimates a resource of 7.75 billion pounds of copper, 150 million pounds of molybdenum, and 32 million ounces of silver.

The Oracle Ridge mine is a small, underground copper mine in the Santa Catalina Mountains just north of Tucson. The mine was operated intermittently, most recently from 1991-1996. The mine is being developed by a junior Canadian mining company, Oracle Ridge Copper (project website).  The company anticipates employing about 200 people to run the mine which has a projected life of 11 years. The mine will produce 140 tons of concentrate (about 30% copper) a day which will be trucked off the mountain and transported to a smelter.

In northern Arizona, near the Grand Canyon are over 1,300 known or suspected breccia pipes many of which contain uranium oxide as well as sulfides of copper, zinc, silver, and other metals. According to the Arizona Geological Survey, “Total breccia-pipe uranium production as of Dec. 31, 2010, has been more than 10,700 metric tons (23.5 million pounds) from nine underground mines, eight of which are north of Grand Canyon near Kanab Creek.”  This area is mired in fears of contamination of the Colorado River (see Uranium mining and its potential impact on Colorado River water) and a 20-year, million-acre mineral entry withdrawal by the Department of the Interior.

In northeastern Arizona there is potential for a major potash deposit. American West Potash has recently delineated, a considerable resource estimated at  158 million metric tons of sylvinite (a mixture of sodium and potassium chloride, not to be confused with sylvanite, a gold telluride), with about 16 million metric tonnes of K2O; and inferred resources of 560 million metric tonnes of sylvinite with just over 66 million metric tons of K2O in the Holbrook Basin, about 30 miles east of Holbrook, Arizona.

The Holbrook Basin area also holds potential for helium and shale oil resources.

Arizona currently has three producing gold mines and several other prospects being actively explored for gold (see here).

“In 2011, the state of Arizona led the United States in the production of gemstones. Arizona has long been famous as a producer of turquoise, peridot and petrified wood. Gemstones such as azurite, chrysocolla and malachite are associated with the Arizona’s many copper deposits and have a long history of being produced there. Agate, amethyst, garnet, jade, jasper, obsidian, onyx, and opal have all been found in Arizona and used to make gems.” –

As you can see, besides currently producing mines, Arizona holds future potential that will add jobs and economic value to the local, state, and national economy – if they can get through the bureaucratic regulatory maze.

Remember, the value of mining is not just the money, it is in providing the products we need to keep our civilization going.  If it can’t be grown, it has to be mined.

Mineral potential of the proposed Sonoran Desert Heritage Area

The Arizona Geological Survey (AZGS) has just published its study of the mineral potential of the Sonoran Desert Heritage Area (see full study here, 25Mb). Establishment of the heritage area, which consists of several detached conservation areas and wilderness areas, would prevent mineral exploration and development on almost one million acres west of Phoenix. A general location map, with mineral potential is shown below:


 The AZGS assessment was limited to the following types of deposits: (1) sand and gravel (aggregates), which are used for concrete and asphalt, (2) porphyry copper deposits, which may yield large amounts of byproduct molybdenum, silver, and gold, (3) gold deposits in veins, some of which contain substantial silver, and (4) manganese deposits.

Some highlights from the report:


“Rapid population growth in the greater Phoenix metropolitan area over the past several decades required enormous amounts of aggregate for construction of new homes, buildings, roads, and other facilities and infrastructure. Once urban development occurs, however, underlying aggregate resources are no longer accessible, and nearby resources may become inaccessible because of concerns about noise, dust, and truck traffic associated with quarry operations. Transportation costs, a major factor in aggregate costs, increase greatly if aggregate must be imported from distant areas.”

AZGS has identified five areas within and adjacent to the Heritage Area that are especially favorable as a supply for much needed aggregates.

Precious metal deposits:

The Harquahala – Big Horn Mountains area, which is included in the Heritage plan, has geology favorable for gold vein deposits. The map below shows the northern part of the area. On the map, orange areas show existing wilderness areas, purple areas show Sonoran Desert Heritage proposed wilderness areas, and the light blue line shows the boundary of the proposed Sonoran Desert Heritage National Conservation Area.


Small mines and prospects within the proposed conservation area have produced 506,000 ounces of gold and 549,000 ounces of silver.

Copper Deposits:

Arizona is the center of one of the world’s three great clusters of porphyry copper deposits

(the other two are in northern and central Chile). At the current copper price, Arizona total copper production from 1874-2010, would be worth $472 billion.

The Big Horn Mountains contain rocks of the right type and age for large copper deposits. Historic mining in the Big Horn Mountains yielded millions of pounds of copper and lead as might be expected for mineralization peripheral to a porphyry copper deposit.

The Gila Bend Mountains to the south are largely covered by younger volcanic rocks. The uncertainty in evaluating the possibility of porphyry copper deposits is high because of this cover, but there are enough indications of mineral deposits, including minor production from the Webb district (27,000 lbs. historic copper production) and scattered evidence of historic prospecting and small mines, that this area is considered to have moderate potential for porphyry copper deposits.


Manganese is used in the production of steel. Currently, the U.S. imports 100% of its manganese. Numerous manganese deposits are scattered over a large region in western Arizona and extend into southeastern California. These deposits are low grade (generally only a few percent Mn) and formed during the past 25 million years. Most historic production occurred between 1953 and 1955 when the US Government purchased manganese at above-market prices. Total historic production is ~100,000 metric tons of manganese (226 million lbs.) from 24 mining districts.

The Aguila manganese mineral district, with 42 million pounds of historic manganese production, is within the proposed SDH National Conservation Area in the northern Big Horn

Mountains. The Black Dome district, with 344 thousand pounds of historic manganese production, is located north of the Hieroglyphic proposed Special Management Area.

Manganese in these districts has not been in economic concentrations historically, but could become so if serious supply disruptions occur and/or prices increase sufficiently, see map below.


The study should be considered an overview assessment. Note that the Arizona Geological Survey is serving as a scientific advisor and is not advocating any position, but I will. The Sonoran Desert Heritage Area proposal, if passed at all, should be reduced to exclude areas with medium to high mineral potential as a matter of economic and national security. If established there should be no additional “buffer areas” adjacent to the heritage area.

See also:

The importance of minerals to our economy and national security