New Mexico Mineral Symposium — Abstracts

History of the silver boom
In the spring of 1860, the Slater party discovered placer gold deposits in California Gulch on the western slopes of the Mosquito Range in Lake County. The gulch was divided into three placer districts:

Arkansas Independent-8,200 ft long (82 claims, beginning at the mouth of the gulch)
Sacramento-19,000 ft long (190 claims, in the mid-portion of the gulch)
California-6,700 ft long (67 claims, in the upper portion of the gulch)

By early summer, 5,000 people had migrated into the gulch. Some mined, some were involved in commerce, and some tried to relieve others of their hard-earned gold through various predatory practices. They occupied crude log cabins, tents, lean-to shelters, or wagons that were strung up and down the length of the gulch. Oro City became the name that was applied to the portions of the gulch in which the Sacramento and California placer districts were located. Placer mining continued through the summer of 1861, when the gold-bearing gravels of the gulch began to be mined out. By the winter of 1862-63 only a handful of prospectors remained, the rest having left to seek other opportunities.

Placer gold production during these years is estimated to have been between 170,000 and 250,000 ounces. Production from several small gold veins on Printer Boy Hill kept mining alive (barely) during the rest of the 1860s and early 70s.

To the east and across the Mosquito Range in Park County, similar placer gold camps at Buckskin Joe and Montgomery went through the same boom-bust cycle. But here a different kind of discovery kept mining alive following the bust in placer gold operations. At altitudes of 13,600 to 13,700 ft on Mt. Bross, Daniel Plummer and Joseph Myers found lead-silver replacement deposits in the Leadville Limestone—the Dwight was located in 1869 and the Moose in 1871. Assays ran from 265 ounces to 879 ounces of silver per ton. Forty tons of ore were shipped to Swansea, Wales, and even with freight charges of $70 per ton, the miners netted a nice profit. The Moose paid from the "grass roots."

During that summer of 1871, several more prospectors made their way to the new Park County silver fields, among them were Sullivan D. Breece and William H. Stephens. A 51-yr-old veteran of mining in the Lake Superior copper country, Stevens plunged into silver mining, learning as he went. Over the next few years he formed a business alliance with several prominent financiers and politicians, a smelter owner, a smelter manager, and a metallurgist. When the alliance soured in 1873, Stevens teamed up with Breece (who had operated a California Gulch placer during the 1860s boom) in several Mt. Bross silver prospects. Breece told Stevens of his continuing belief in the California Gulch placers, provided that a water shortage problem could be overcome. During this time, Stevens convinced Alvinus B. Wood, a former associate from his Michigan mining days, to join him in Colorado.

California Gulch is, at best, an intermittent stream carrying a very low water volume. In fact, it has no flow during much of the year. So, Stephens and Wood (with Breece as a partner) formed the Oro Mining Ditch and Fluming Company. Stevens then traveled back east during the winter of 1873-74 where he raised $50,000 for a California Gulch placer mining venture. The men used the money to dig an 11-mi ditch from the Arkansas River to provide water for hydraulic giants like those that had proven so successful (and environmentally destructive) in California. Having gained control of the old gulch claims, they began placer operations. It was a limited success. There was gold aplenty, but they had to spend an inordinate amount of time cleaning out the heavy brown sands that clogged their sluices. This was not a new problem in California Gulch; those same sands had plagued the placer operations of the early 1860s.

As it turned out, the much-cursed dark sand was composed of the lead carbonate mineral cerussite combined with various iron and manganese oxides. The material was too heavy to wash through the sluices with the "ordinary" sands; instead it filled the spaces between the gold-catching riffles (small strips of wood nailed to the bottom of the sluice box every few inches). With those spaces between the riffles filled, the gold-trapping mechanism of the sluice was negated and the sluice failed to trap gold.

Stevens recognized the cerussite because that mineral was the primary ore in the oxidized portion of Park County silver mines—the cerussite carried significant amounts of silver as a contaminant. Assays soon confirmed that this California Gulch cerussite also carried silver, and in 1874 the partners began a prospecting effort that continued into 1876. They discovered lead-silver replacement deposits in the Leadville Limestone cropping out around the western and southern slopes of Iron Hill. They staked a series of claims on these mineralized outcrops and founded the Iron Silver Mining Company. This was the beginning of the Leadville silver boom.

For a time the local populace did not catch on to the significance of the Stevens-Wood discoveries, but then three emigrant Irish brothers, John, Charles, and Patrick Gallagher, staked the Camp Bird and Keystone claims on near-surface mineralization on the north slope of Iron Hill. Lore has it that they dug where Stevens told them to dig. According to that local lore, Stevens was more concerned with getting the brothers out from underfoot than with passing on a useful prospecting tip. No matter Stevens' motives, the Gallaghers struck ore very near the surface and had soon staked their claims.

Although completely ignorant of "proper" mining techniques, the Gallaghers soon mined out enough ore to raise their standard of living by several orders of magnitude. They then sold their entire group of claims to the Argentine Silver Mining Company (founded by Edwin Harrison of the St. Louis Smelting and Refining Co.) for $225,000. The Gallaghers split the purchase price and went their separate ways to see the world, and enjoy the seeing. The story of how three poor Irish emigrants had struck it rich was the stuff of fairy tales. Accordingly, it received a great deal of attention from the newspapers of the day, and this publicity did as much to fan the flames of the Leadville silver boom as any other single occurrence.

More discoveries followed, first at other locations on Iron Hill, and then on Carbonate Hill, just to the west. On Carbonate Hill, the original discovery was the Carbonate, located in June 1877 by Nelson Hallock and Albert Cooper. The Yankee Doodle, Crescent, Catalpa, and Morning Star were staked soon thereafter. The Morning Star was the real prize among them. It was sold to Governor John L. Routt in October 1877. After faithfully working the property for 2 yrs, an immense orebody was found. Production during the last half of 1879 was $290,491, and averaged $70,000 per month for the first
3 mos of 1880. The holdings of the Morning Star Consolidated Mining Company were sold for $1,000,000.

The climax of the Leadville silver boom arrived with the discoveries on Fryer Hill. George Fryer and John Borden filed on the New Discovery on April 4, 1878. Borden sold out to Foss Bissell and A.V. Hunter, and Fryer sold out to Jerome Chaffee for $50,000. On April 15 August Rische and George Hook got a grubstake from Horace Tabor and began prospecting near the New Discovery. They had to go back for two more grubstakes before finding ore at 28 ft in their prospect shaft. They named the claim Little Pittsburg in honor of Hook's hometown. When the two reported to the Tabors that the assay ran $200 per ton, Augusta replied, "Rische, when you bring me money instead of rocks, then I'll believe you." Hook sold out to Rische and Tabor for $90,000; Rische sold out to Tabor and David Moffat for $265,000. The Little Pittsburg Consolidated Mining Company was incorporated with Chaffee as President, Moffat as Vice President; and Tabor and Borden on the Board of Directors. Tabor sold out for $1,000,000.

By February 1880 the Little Pittsburg high grade ore was nearly exhausted. Chaffee and Moffat dumped 51,000 shares of stock before the bottom fell out in mid-March. The stock fell from $34 a share to $7.50. Those were different days. New York stockbrokers praised Moffat for his "superior shrewdness in standing from under," meaning that he had been able to dump his shares (undetected) before the price crashed.

The Chrysolite was located on May 3, 1878, by "Chicken" Bill Lovell, with Fryer and Borden each owning one quarter. Lovell salted the prospect shaft with ore from the Little Pittsburg and sold one-quarter interest to Tabor for $10,000 on July 13. The rest of the transaction was not recorded, but the Chrysolite Silver Mining Company, Inc., produced more than $1,700,000 before its stock crashed in 1880.

Tabor purchased the Matchless mine outright for $117,000. It produced $2,000 per day for a considerable period of time. The property became famous as the final home for Tabor's second wife, "Baby Doe," in the poverty-stricken years of her widowhood.

Many believed the Robert E. Lee to be the richest Fryer Hill mine of all. Located in June 1878 the mine passed through many hands during the boom years. Over $250,000 was produced during a 39-day period in 1879. Another orebody produced $118,500 in a 17-hr mining effort.

Geology and mineralogy of the Leadville silver deposits
The Leadville district is located on the eastern limb of the Sawatch uplift in the central portion of the Colorado mineral belt. Paleozoic sedimentary rocks lie unconformably atop Precambrian metamorphic and igneous rocks. The Mississippian Leadville Formation (which is composed of the lower Redcliff Member and the upper Castle Butte Member) is the major host rock for the rich lead/silver manto orebodies mined during the years of the silver boom.

The carbonate sediments of the Leadville Formation were dolomitized during diagenesis. A Late Mississippian global sea-level drop exposed the Leadville Formation to erosion. Over time, a karst erosion surface developed, complete with caves, sinkholes, solution breccias, and solution enlarged joints. Both dolomitization and karstification enhanced the porosity and permeability of the Leadville Formation, and may have influenced the path that migrating fluids followed.

Ore-forming solutions generated during intrusion and emplacement of stocks at Printer Boy and Breece Hills traveled through the permeable beds at about 39.6 m.y. ago (± 1.7 m.y.), depositing a suite of primary sulfide minerals. Orebodies are mostly confined to the more permeable beds of the dolomite. Primary minerals containing silver are galena (as a contaminant), and, to a lesser extent, argentite/ acanthite and tetrahedrite.

Following uplift and erosion, prolonged weathering oxidized the upper portion of many orebodies in the district, producing supergene cerussite and anglesite (containing silver as a contaminant), chlorargyrite, chlorargyrite variety embolite, silver, and argentojarosite.

Production of these supergene minerals accounts for the great Leadville silver boom of the 1870s and 80s.