Saturday, October 15, 2016

The Golden Gate Stamp Mill

High up in the Sierras above Walker Valley, outside Bridgeport, is a dilapidated old stamp mill. It is the last stamp mill managed by the Bishop BLM office, and is a remarkable site because of its scale. Only ten stamps were ever used here, and ten remain, but they are the largest stamps I have ever seen, and the beams that are used to build the mill are colossal old growth wood, 11x22 inches. Each stamp (it's said) weighs 900 pounds, and is at least ten inches in diameter.

The mill was destroyed by avalanches numerous times over the last hundred years, and this structure was built around 1900. It has suffered significant structural damage, and stabilization work took place over three months in 2005 in hopes of keeping it standing through more heavy Sierra winters. Not much else remains besides the mill, cookhouse, and bunkhouse. The arial tramway's remains lay close by, but the mine openings are nearly inaccessible without great tenacity, as they sit 2300 feet above on the mountainside. There were three tunnels, totaling a couple thousand feet of workings. The outbuildings were destroyed in the fatal avalanches in 1911, and everything was rebuilt a few hundred feet away below a lesser slope.

The two stamp batteries.

Missing one, oddly. The stamp case is huge!

Driving wheels up top. These wheels had a belt that went to the bull wheel driving the stamps.

Cam shaft and stamps

Ore feeder to the back of the stamp case, where it was ground up with water or mercury into an amalgam.

Hand for scale. Stamps are the largest I've ever seen. I estimated 10 inches across.

The backside of the stamp battery shows how it's ready to slump forward. It was stabilized in 2005.

Large mortise and tenon joints holding the ore bin up.

These are the main wheels that powered the mill. The belt ran to a small peloton wheel.

Ore bin

Pelton water wheel case.

Different angle. The bull wheels on stamp mills are always wood because metal wheels shatter with the vibration.

Very informative interpretive sign from the BLM. Click to enlarge.

Remains from the arial tramway terminal.

Tramway cable.

Looking up the stamps at the camshaft. Oddly, didn't show very much wear.

Workshop. Full of poison oak.

Former cookhouse and bunkhouse. It has collapsed, sadly.

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