Hard Rock Mining Tour: Cardinal Mill

Cardinal Mill

Getting There

This site is closed to the public for safety reasons

After failing to strike it rich in California, prospector Stephen Conger decided to try his luck in the mountains of Boulder County. In 1870, while following the profitable gold and silver vein of the Caribou Mine, Conger found another readily-accessible lode. He called it the Boulder County Mine.

Cardinal City

Drawing miners by the dozens to the area, a small town quickly grew around the Boulder County Mine. Cardinal City, as it was known then, was located on the wagon route between Nederland and the booming mining town of Caribou. But while Caribou was orderly, Cardinal City was rough and tumble with its brothels, saloons, and gamblers. About 10 years after its founding, Cardinal City became an 1880s mining metropolis with around 1,500 residents. But Conger had other plans.


Conger soon realized that the best ore lay deeper within the hillside. Instead of digging down to reach the ore, Conger began driving a tunnel into the side of the hill to undercut the vein from below. A new town called Cardinal grew around the new mine, and Cardinal City, now called Old Cardinal, fell on hard times. To make matters worse, in 1904 the Switzerland Trail of America neglected to make Old Cardinal a stop on their railroad, favoring the newer version of the town.

The Mill

Built at the mouth of the Boulder County tunnel in 1903, Cardinal Mill used a new metal extraction procedure involving cyanide. The use of harmful chemicals, giant conveyor belts, and loud machines, made working in a mill an extremely hazardous profession. Also, the ore from the Boulder County vein was too complex for the Cardinal Mill to effectively process without better technology. Instead, the mill's operators turned to tungsten. Between 1905 and 1910, Cardinal was one of only five full-time tungsten mills in the region. The mill went back to gold processing in 1914, and operated on-and-off until 1942.


Boulder County purchased Cardinal Mill in April 2003 with the intent to preserve the building for the education and appreciation of future generations. Read more...

Did You Know?

Tungsten, Swedish for "heavy stone," was used in the early 1900s in light bulb filaments and to harden steel. It is harder than titanium, nearly as dense as gold, and has the highest melting point of any non-alloyed metal! Today it is used in armor-piercing ammunition and is popular in jewelry.


Panoramic Video

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