Tintic Mines and Mills

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This page was last updated on September 5, 2025.

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Overview

The USGS Professional Paper 107, Tintic Mining District, published in 1919, on page 116 listed the following mills "pan-amalgamation plants" as of 1895.

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 an object to ship instead of mill, and so all the milling plants were soon closed.

Tintic Mines and Mills

Links to separate pages about the most important and successful Tintic mines and mills that depended on railroads to ship their ores and concentrates.

Centennial-Eureka Mine and Mill

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

Grand Central Mine

Grand Central Mine -- Information about the Grand Central mine in Mammoth Hollow in the Tintic Mining District.

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

Ajax Mine

Ajax Mine and Mill -- Information about the Ajax mine, including its predecessor companies.

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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