Tintic Mills

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This page was last updated on October 9, 2025.

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Overview

(The focus of this information is to describe the reduction and concentrating mills at Tintic that used railroad transportation, using sources not previously readily available.)

The Tintic Mining District in central Utah was the home of some of the richest silver mines in the West. The first silver ore was discovered in 1869 by George Rust, a cowboy herding cattle in Ruby Hollow, three miles south of what would later be the town of Eureka. Word soon spread and many other mines were very soon being developed. Those early miners organized the Tintic Mining District in December 1869, taking its name from the large open valley to the west. The first successful Tintic mines came in the early months of 1870, and included mines all along the western slopes of the East Tintic Mountains, from north to south, mines in Eureka, Mammoth Hollow, Ruby Hollow, and Diamond Gulch. Eureka came into being as the area surrounding the Eureka Hill mine was developed.

The early mills in the Tintic district date from 1872 to 1893, when the Mammoth mill opened in Mammoth Hollow near the Mammoth mine.

(The first railroad to the Tintic District, by a Union Pacific subsidiary known as the Salt Lake & Western, arrived in June 1882, at what became known as Ironton, out in the Tintic Valley. In August 1883, a three-mile branch was built to Silver City, and in September 1889 a branch was completed to Eureka. The Tintic Range Railway, a subsidiary of Rio Grande Western, arrived at Eureka from the east in early December 1891, and was extended to Silver City in May 1892. Joint trackage to Mammoth was completed in December 1893.)

Early Tintic Mills

There were several early mills built during the Tintic district's early years, 1872 to the mid-1890s, before the large Mammoth and Sioux mills were built in 1894-1895.

(Read more about the Early Tintic Mills)

Tintic Mills

The Mammoth and Farrell mills were at Robinson. They operated very successfully on the lower-grade ores of the district and shipped both bullion and concentrates. The richer ores were shipped to the smelters·in the vicinity of Salt Lake City and elsewhere. Later the smelters and ore buyers offered better prices and the railroads lower rates on some of the ores that were being milled, making it easier and cheaper to ship milling ores instead of milling to concentrates, the shipping the concentrates, and so most of not all mills at Tintic were soon closed.

(The Mammoth mill was completed in January 1894, and had direct railroad service by two railroads by way of the newly completed joint trackage. The Sioux-Farrell mill, adjacent to the Mammoth mill, was completed in January 1896.)

The following is a list of active mills in the Tintic district in 1895.

Centennial-Eureka Mine and Mill

Centennial-Eureka -- Information about the Centennial-Eureka mine, including its predecessor companies.

Mammoth Mine and Mill

Mammoth Mine and Mill -- Information about the Mammoth mine and mill, including information about its predecessor companies.

Sioux Mine and Mill

Sioux Mine and Mill -- Information about the Sioux mine and mill, including information about its predecessor companies, and the Sioux-Ajax Tunnel.

Other Mills

The May Day mill construction started during the last week of January 1901, with the beginning of excavation. Work was completed by mid-May 1901, with the construction crews moving to the building of a mill for the Yankee Consolidated company. The May Day mill was closed briefly during August 1901 to strengthen the building structure, which had proved insufficient for the mill operations. Repairs were completed and a public open house was held in mid-November 1901. The process being used was known as "Wood dry process of concentration" with air being used to fluidize the flow rather than water. The mill was closed between May and October 1902 to make changes to the milling process, with the May Day mill in Eureka being to only mill at that time using the Wood process, invented by C. S. Wood of San Francisco. The mill's capacity was increased from 60 tons per day, to 100 tons per day in June 1907. (Salt Lake Mining Review, January 30, 1901; May 15, 1901; August 30, 1901; November 30, 1901, describes the process; May 15, 1902, October 30, 1902; June 15, 1907)

Glossary

Mining Terms and Glossary -- A separate page with an abbreviated list of mining terms used in describing the mineral mines of Bingham and Tintic, and the coal mines of Carbon and Emery counties. The larger PDF version was compiled by the U. S. Bureau of Mines in 1968.

The mines of the Tintic District were predominately gold and silver mines, with a large amounts of copper and iron. To compare, the mines of the Park City and Cottonwood districts, were predominately lead and silver mines. The mines of of the Bingham District were predominately lead, silver and copper mines.

Research suggests that there was a constant discussion and disagreement among milling men as to the best method to separate precious metals from the raw ore that was extracted from the mines. The owners and investors were constantly looking to increase the yield from their mills, which resulted in a regular change of mill managers and superintendents, as the popularity of various processes came and went.

There were many methods used to separate metals from the base rock of the raw-mined ore. The most well-known was smelting, with its numerous processes to obtain gold, silver, copper and lead. Smelting worked best for the most valuable ore, usually known as first-class ore, or smelting ore. Smelting itself was the subject of constant improvement, and still is today.

Other methods involved less valuable ore, known as second-class, or milling ore, which always needed some form of reduction or concentrating. There were many methods of reduction, including gravity treatment with jigs, shaking tables, centrifugal spirals, Frue vanners, sluices, leach treatment, and the later froth flotation by use of chemical reagents. Gravity treatments involved taking advantage of metals being heavier then the surrounding native rock. Prior to any reduction or concentration treatment, the ore needed to be crushed to a fine powder, usually to fit through a 40-mesh screen, which was a screen with 40 openings per inch.

In the early days of Utah gold mining and milling, 1870 to 1900, all the mills used some version of vanners and amalgamation tables, with changes in the details of hardware design and reduction processes as promoted by numerous sources. Most of the early reduction methods were amazingly inefficient, which resulted in later years of their dumps and tailings ponds being re-processed to recover metals that had passed through the early processes.

(Read the Wikipedia article about Ore Processing)

Vanner

A vanner is a type of gravity-based concentrating machine used in mining to separate finely-crushed, heavy mineral particles (like precious metals) from lighter waste material, known as tailings.

The most well-known machine of this type is the Frue vanner, which was invented in 1874. A Frue vanner was an ore-dressing apparatus consisting essentially of a rubber belt traveling up a slight inclination. The material to be treated is deposited at the lower end of the moving belt and is washed by a constant flow of water while the entire belt is meanwhile shaken from side to side. The belt has shallow ridges at a slight downward angle across the belt that gather the tailings off the one side, while the heavier metals remain.

On a Frue Vanner, finely crushed ore, mixed with water in the form of a slurry is fed onto the lower end of moving, shaking belt. As the pulp travels up the incline, water is sprayed over it. The rapid shaking and water wash away the lighter waste material. known as gangue or tailings. The heavier mineral particles, such as gold and silver, are trapped by the rubber belt's flanges and the surface action. The valuable, heavy mineral concentrate continues to adhere to the belt as it moves upward and passes over the top roller. At the top, the reduced material drops into a collection box containing water.

The reduced material is then sent to the vanners to gather the precious metals by the amalgamation process.

(Read the Wikipedia article about Vanning and Vanners)

Amalgamation

Amalgamation is a process used to extract metals from their ores by mixing them with mercury. This mixing took place on copper sheets, or "pans" coated with liquid mercury. The gold (and silver) was attracted to the mercury forming an "amalgam" while the waste material passed over the mercury. This method is particularly useful for the extraction of precious metals like gold and silver. The amalgam, in the form of a paste or "pulp" was then scraped off the copper plate. The mercury was then renewed on the copper plate and the process repeated. The amalgam pulp containing mercury, gold and silver was then heated in a closed container or vessel known as a retort, which vaporized the mercury. The mercury vapor was cooled, returning the mercury back to its liquid state.

After the mercury was removed by vaporizing in the retort, what remained was a combination of almost pure gold and silver in the form a foam or "sponge" that was then melted to create bullion bars.

Many of the Tintic ores also contained copper. Amalgamation does not work for copper, so only a limited number of Tintic mills, such as the Mammoth and the Sioux-Farrell, used amalgamation.

Beginning in the 1890s, amalgamation began to be replaced in the recovery of gold by the cyanide process.

(Read the Wikipedia article about the Gold and Cyanide Process)

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