Bat Cave mine

Several unsuccessful early attempts were made to mine the nitrogen-rich guano deposit within the cave for fertilizer.

Based on a reputable mining engineer's estimate that the cave contained 100,000 tons of guano, the company constructed an elaborate plan to extract it.

A small airstrip was built on a nearby sandbar in the Colorado River, and all supplies and machinery needed were flown in.

The mining engineer's estimate of the potential size of the guano deposit proved wildly optimistic: the cave contained only about 1,000 tons of minable material.

Paleontologist Paul S. Martin and a colleague visited the mine in 1958, after reading a report in the New York Times that mentioned the guano came from "giant, meat-eating bats millions of years ago."

Martin collected a sample from 7 ft (2m) below the surface of the guano, which yielded a radiocarbon date of 12,900 ± 1,500 years ago.

As of 2007, some remnants of the old operation remain at Bat Cave,[3] and on the West Rim in the Hualapai Indian Reservation.

Aerial view of Guano Point. Old tramway headhouse is at the end of dirt road (right). Second tramway tower is more clearly visible, on skyline to right. Bat Cave mine is 2,500 feet (760 m) below, across the canyon.