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Mine Tales: Dredges helped Arizona dig up gold

The word “dredging” might not make your heart race, but it certainly helped speed the pace of mining in Arizona.

From the 1900s through the 1930s, large-scale extraction of the placers on the Prescott area’s Lynx Creek occurred in the form of dredging to remove gold from river-flat gravel deposits with little grade.

A technique used in the New Zealand placers in 1882 and first employed in North America at Bannack, Montana, in 1897, dredging was used effectively in the gold fields of California and Alaska.

The steam dredge functioned as a floating processing plant on water. It excavated alluvial sands directly in its path, while digging its own river through a streambed.

Built along the river, dredges were initially expensive to assemble, but they required little maintenance after that.

Typical dredge design included a flat-bottomed, shallow-draft hull, separation equipment, a steam engine — and a giant shovel with an endless bucket-belt scoop “ladder” that displaced sand on a conveyer belt, transporting it to a separation area onboard composed of riffle boxes and tables.

The oversized gravel was deposited in the back bank of the dredging pond via a rubber conveyor belt. The finer material was distributed for further separation of gold by equipment similar to a sluice box and a rocker.

As its means of propulsion, the dredge was winched forward with cables secured to anchors or trees, digging its own river as it moved forward through the alluvial sands.

Ideal topography for dredging included a low mean grade and a broad alluvial overburden found in the lower stream valleys. When a dredge hit a solid rock ledge, embedded tree trunks, abandoned mine workings or exhausted a stream bed, it was rendered ineffective as it could not reverse its course. As a result, it was cannibalized for parts and then abandoned.

One example of a dredge operation in Arizona was the Gold Gulch Mining Co.’s dry-land dredge operation in the Teviston district, at the northern foot of Cochise County’s Dos Cabezas Mountains. The dredge’s rated capacity was 50 cubic yards of gravel per hour, consuming 150 gallons of water a minute.

Operated between 1937 and 1940, it contributed to the output of placer gold valued at $17,696 from both the Teviston and Dos Cabezas placers. Yielding profit at depths between 3 to 10 feet between 1933 and 1947, the 300-acre property included its largest gold nugget valued at $375.

A more profitable placer gold operation was in the Bradshaw Mountains at Lynx Creek. Consisting of more than 16 miles of placer gold deposits, Lynx Creek — discovered by Capt. Joseph R. Walker and a party of California miners — was worked over the years by pans, hand rockers and small sluices. The rich gravels yielded an average of $20 of gold a day before 1885.

During the 1890s, soldier of fortune Thomas G. Barlow Massicks conducted hydraulic mining of the gravels at Lynx Creek, including building a dam that was soon destroyed by a flood.

Dredging began with the Speck Co. whose dredge — later operated by F.G. Fitzmaurice of Prescott in the early 1900s — produced negligible results in the form of $800 before breaking down.

Considered the largest producer of placer gold in Arizona, the property was later worked by the Lynx Creek Placer Mine Co. from 1934 to 1940 and included a floating washing plant and two draglines.

During the Great Depression, more than 600 men worked the Lynx Creek placers, making 50 cents a day in 1934 by rocking and sluicing the gulches of upper Lynx Creek.

The Harper Brothers & McGuire Co. dredge worked lower Lynx Creek for 6 miles, mining the gold left behind from the Hassayampers, who mined its gravels in 1863.

Production figures prior to 1885 and again from 1933 to 1942 from Lynx Creek were estimated at $2 million in gold.

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