August 2007

Economic Geology

California here we come (Part 19)

By R. J. Cathro

Hydraulic mining for alluvial gold, Trinity County, CA. Eastman Collection B-921 | Courtesy of the University of California Davis

“The Mexican-American War may well be a textbook example of the mining engineers’s adage that commerce follows the flag, but the flag follows the pick ... High officials in Washington ... knew that California possessed gold, and much else besides, before declaring war on their neighbor. In 1843, nearly two thousand ounces of the metal were sent to the United States from mines discovered near the San Fernando Mission in southern California. Rumors kept leaking out that the sparsely populated territiories of northern Mexico possessed mineral riches comparable to those found in the southern half of the country.” (Brechin, 1999)

Economic geology and mining entered a new and modern stage following the California Gold Rush in 1848-49. Although the placer gold discovery didn’t have any direct impact on the study of economic geology by itself, the rush occurred in the right place, and at the right time, to trigger unprecedented advances in scientific study, working conditions, entrepreneurial activity, and the communication of ideas. These coincident trends would prove to have major social, economic, and political impacts, initially in North America, Europe, and Australia, and subsequently worldwide.

At the time of the Gold Rush, the U.S. mining industry was in an embryonic stage, mainly exploiting small scattered deposits along the East Coast that only served local markets. Most metals and manufactured goods were still imported from England and Europe. The earliest mining developments, including copper at Simsbury, Connecticut; Hanover and New Brunswick, New Jersey; and Orange County, Vermont, between 1709 and 1820, were summarized by Rickard (1932). Iron ore was discovered at Roanoke, North Carolina, in 1585 and at Jamestown, Virginia, in 1608, and was mined from scattered small deposits of bog iron, but the first cast-iron wasn’t produced until 1727 from a deposit at Coventry, Pennsylvania. The great iron deposits near Lake Superior, first mentioned in 1840, weren’t exploited until large coal deposits were discovered later.

Lead, which was a vital economic metal at the time, was discovered in 1621 near Jamestown, Virginia, and small occurrences were mined briefly at Ancram, New York; Southhampton, Massachusetts; and in Maine, Connecticut, and Pennsylvania. The first lead discovery of any significance was the Upper Mississippi District, which was recognized by French Canadian fur traders as early as 1687, when they obtained lead for bullets from Native Americans living along the Mississippi River (then part of the French Territory of Louisiana). It was exposed in galena veins along the river in the vicinity of Dubuque, Iowa, and Galena, Illinois, at the edge of a large district that extends into southwestern Wisconsin. While it developed into an important source of the metal by the 1840s, it proved to be richer in zinc, a metal that was not then in great demand. Lead mining gradually shifted to the Southeast Missouri Lead District, where the Mine Lamotte had been opened by another French company in 1720. It is located about 150 kilometres downstream, just south of St. Louis. A much larger zinc-lead camp situated farther southwest, straddling the boundary between Missouri, Kansas, and Oklahoma (called the Tri-State District), was discovered about 1810 and first mined in 1848. Because it is also zinc-rich (zinc/lead ratio of about 5), major development was delayed until the zinc market became stronger after 1870 (Snyder, 1968).

Zinc and lead mineralization is similar in these three large districts, as well as in several smaller ones nearby. It constitutes of an economically important and distinctive family of world-class deposits named the Mississippi-Valley type. These ores form stratiform to semi-conformable, massive, irregular sulphide bodies within particular facies of dolomitic limestone horizons. They are mostly confined to single stratigraphic units within each camp and range in age from lower Cambrian to Pennsylvanian. Mineralization is usually composed of galena, sphalerite, and pyrite with minor amounts of silver or copper. Veins are commonly present but only account for a small proportion of the ore. Because the mineralization had no apparent relationship to plutonic or volcanic activity, it couldn’t be easily reconciled with the contemporary hydrothermal theories. It was the first new deposit type and mineralized geological setting discovered outside Europe and it became the subject of intensive scientific research over the next century. However, it would be a long time before the genesis of the metals could be explained.

Prior to the California Gold Rush, very little gold or silver had been discovered in the United States. Small amounts of placer gold were found in Appalachia, beginning with the Reed Mine in North Carolina in 1799. From 1804 to 1866, total placer production from this goldfield, extending across five states (Virginia, the Carolinas, Georgia, and Alabama), amounted to about $19 million.

Geological research in England in the early 1800s had evolved into a clubby study of stratigraphy and paleontology that treated mineral deposits with condescension (see Part 18, June/July 2007 issue, CIM Magazine). Aside from coal, no important new mining districts had been discovered in Western Europe or Great Britain for centuries, and the study of economic geology had become lethargic and uninspired. The California Gold Rush would soon lead to the discovery of new types of mineral deposits that would challenge old theories; would require advances in mining techniques, technology, and transportation; would stimulate worldwide migration, industrial activity, and increased demand for metals; would provide better prospecting and economic opportunities for miners than at any time since the 14th or 15th centuries in the Erzgebirge and Cornwall; would produce new institutions for advanced training of mining engineers and geologists; and would require the creation of new types of international communication, including technical newspapers, scientific journals, and professional organizations.

Strange as it may seem today, gold had been found in California many years before the Gold Rush (Rickard, 1932). The earliest published report in English was probably one written by Robert Jameson (1816) (yes, the same Edinburgh professor who made such a poor impression on Charles Darwin - see Part 17, May 2007 issue, CIM Magazine). He stated: “On the coast of California, there is a plain fourteen leagues in extent, covered with alluvial deposits, in which lumps of gold are dispersed.” Other reports, including one published in Mexico City in 1842 by a former deputy of the Mexican Congress, confirmed this gold discovery and others. Rickard speculated that these stories were ignored or suppressed because the U.S. government was already anticipating a change of national ownership of the region to mark the end of a war with Mexico. That occurred with the signing of the Treaty of Guadalupe Hidalgo on February 2, 1848, under which the U.S. annexed most of northern Mexico, including California, New Mexico, Arizona, Nevada, Utah, and parts of Colorado and Wyoming for $15 million. The following year, California produced gold worth three times as much as the payment to Mexico.

The treaty was actually signed nine days after the event that is generally regarded as the start of the rush, the recognition by James W. Marshall, a carpenter building a water-powered sawmill, of a gold nugget encrusted with quartz. By the time the first public notice appeared in a San Francisco newspaper on March 15, the stampede to the goldbelt by some of the 15,000 people then living in the state was already well underway because the gold belonged to whoever found it - tax-free. Within two years, over 300,000 people had arrived by the arduous and dangerous overland route from the eastern United States and Canada, or by the hazardous ocean voyage around Cape Horn, or across the Pacific Ocean. Known as Forty-Niners, they began frantically exploring a belt about 300 kilometres long as soon as they arrived. Naturally, most of them were unlucky and either drifted into more traditional lines of work, wandered off to prospect elsewhere, or returned home. It has been estimated that the total value of the gold recovered between 1850 and 1859 was approximately $560 million, an average of about $250 per miner. Summaries of the California Gold Rush are available online from the television program American Experience (2006) and from Wikipedia (2007). Another valuable reference is Paul (1947).

Marshall’s discovery (or rediscovery) was made at Coloma, about 50 kilometres southeast of Sacramento (Sutter’s Fort), on the South Fork of the American River. Because California was under U.S. military rule at the time after the signing of the treaty, and no mining code had been written, the prospectors and miners proceeded to draft their own mining laws, a remarkable example of self-government. Because many of those with mining experience were from Europe or the United Kingdom, or from mining districts in the United States or Mexico that had been developed by Europeans, the new rules were generally patterned after those in force in Germany, Cornwall, and Mexico. George Hearst, who had grown up on a farm in the Southeast Missouri Lead District and developed a keen interest in mining and geology from the nearby French miners, recalled in his unpublished memoirs (Robinson, 1991) that miners from his state had a strong influence on the rules that were developed in the California placer gold camps.

The rules written by the California placer miners, and later adopted throughout the western states, were subsequently deemed to be so sensible that they formed the substance of the U.S. mining law enacted by the U.S. Congress in 1866. Unfortunately for the mining industry, the U.S. law also included the worst feature of the German code, known as the Apex Law, under which the owner of the outcrop of a vein was entitled to the ownership of that vein as far down the dip as it could be followed. This rule, which had also been adopted in Derbyshire (developed by miners from Germany), was only workable in vein districts that consisted of simple veins or were controlled by one owner. It wasn’t used in Cornwall, Latin America, Canada, or most other parts of the world where the boundaries of a claim are projected vertically downward. The Apex Law caused frustrating problems for miners, who could not always be certain if a vein they intersected underground might not be a branch of another vein already claimed by someone else. As a result, American mine owners were continually involved in legal disputes, and a large number of geologists, mining engineers, and lawyers built profitable careers as apex litigators. The 12 leading mines in the Comstock district, Nevada, for example, were embroiled in a total of 245 lawsuits for five years costing about $10 million, roughly one-fifth of the entire output of the camp during that period. In one case settled in the Helena, Montana, district court in 1893, expert witness fees alone were more than $100,000, a large amount of money at the time (Spence, 1970).

One of the main consequences of the discovery of gold in California was the invaluable financial assistance it gave to the North during the U.S. Civil War (1861-65). The value of the gold and silver shipped from the western states during the years 1861-64 (inclusive), $186 million, was vitally important in enabling the United States to remain a single nation and thus had a profound effect on world history. On the downside, the Gold Rush created severe racial, ethnic, and environmental clashes.

Among those who joined the rush to California was an Englishman, Edward H. Hargraves, who arrived from his home in Sydney, Australia, in October 1849. Although he did fairly well as a prospector, he hurried back to New South Wales after becoming convinced that a similar geological setting existed there. Within a month of his arrival on February 12, 1851, he discovered gold at Bathurst, on the Macquarrie River, 250 kilometres northwest of Sydney. That triggered the great Australian Gold Rush, which marked the beginning of the mining industry of Australia and contributed to the growth in population from 430,000 in 1851 to 1.7 million in 1871

The great California and Australia gold rushes were not the first that the world had experienced. That ‘honour’ belongs to New Spain and the Spanish conquistadores, those footloose and ruthless mercenaries idled by the end of the Moorish wars, who conquered and plundered the Aztecs and Mayans in Mexico and the Incas, centered in Peru, between 1519 and 1550. After they had stolen the possessions of the living, they proceeded to rob the graves of their ancestors. In addition to the creation of the Spanish Empire, the plundering led to the the rediscovery of indigenous minesites and eventually to the discovery of most of the great Mexican silver districts, between approximately 1546 and 1600. In spite of the Spanish expertise in exploration and mining, and the availablility of Agricola’s books, the Spanish made only negligible contributions to the scientific investigation of mineral deposits (Cathro, 2000).

The California placer miners tackled the immense opportunity presented by the huge goldfield with typical American entrepreneurial spirit and quickly developed a number of technical improvements to hydraulic mining that were adopted around the world, including in the Cariboo and Klondike goldfields in Canada. By 1849, gold veins had been discovered within the placer district and lode mining had commenced. The geology and mining history of the three major bedrock sources, the Mother Lode vein system, Grass Valley – Nevada City camp, and Alleghany camp, as well as the introduction of dredging, will be described in subsequent chapters.

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