The Ingersoll Mine is well-preserved compared to other Black Hills mines and ghost towns. The buildings and mine are a short and easy hike from the parking area. The mill has several stories and all can be accessed. In several places, the floor has fallen through so proceed with caution. The highest floor can only be reached by climbing a few dozen thin wooden stairs. Several have been spray painted with frowning faces, indicating that it will break soon. The mine itself doesn’t go very deep into the mountain, but you’re still going to need a flashlight.
The Ingersoll Mine (also known as the Bob Ingersoll Mine, Horace Greeley Mine, and Ben Butler Mine) was discovered on August 24, 1880 by John W. Okey, John Schofield, and R.G. Williams.
In his paper, “A Mine With More Varieties than Heinz Has Pickles”, head mining engineer A.I. Johnson concisely described the Ingersoll Mine as “a mecca for geologists and a paradise for rock hounds.”
The most common, economically viable minerals found were feldspar and mica. Shockingly, about 2,200 tons of mica was produced at the site.
Beryl, a rare mineral, was plentiful in the Ingersoll Mine. Beryl can be found in crystals that vary greatly in size. The six-sided crystals are colorless when pure, but impurities can tint it colors like green, blue, yellow, red, or white. Emeralds are simply green beryl. In 1915, a large beryl crystal was found at the mine, measuring 44 inches high and 8 feet long. An even larger crystal was found in 1942 that was 19 feet long.
“Dr. Hess, head of the Rare Minerals Division of the Bureau of Mines, visited the site and wanted to make a national monument of the [large 1942 crystal] but, because of the strategic importance of beryl in the war effort, the crystal was mined and sold,” recalled Johnson.
The fall of 1944 was the stage for the mine’s largest ever beryl discovery. A crystal was found that was 28 feet long with faces being about 8 feet by 8 feet. Over 64 tons of beryl were mined from this crystal.
The Ingersoll Mine was also a large producer of lepidolite, a mineral used in glass manufacturing. About 9000 tons were mined and milled at this site. Lepidolite from this mine was used in making Pyrex ware and in a lens at the observatory in Mt. Wilson, California.
A mill for processing lepidolite was built in 1942 and closed only two years later. Johnson attributes this to “foreign sources [making] production uneconomical.” Despite its early closure, he still considered the mill groundbreaking.
“The mill at the Ingersoll for processing lepidolite and its by-products was the first and only one of its kind in the world,” wrote Johnson.
The mineral uraninite, a source of radium, was found here. A sample was taken by Dr. Hess from the Ingersoll Mine and used to make an age determination of the Black Hills. The results concluded that the Black Hills was 1620 million years old, give or take 20 million years!
Interest in the site gradually waned as minerals were depleted, and it slowly became abandoned. During the Ingersoll Mine’s fascinating history, over 60 different minerals were mined here.
In the past few months, the landowners opened the site for tourists to try their hand at prospecting and tour the old mine. Rates are abnormally high and no mill access is allowed, but hopefully it will open again for urban exploration after tourist season!
The trailhead can be found a few miles outside Keystone on Old Hill City Road. Driving into Keystone, take a right onto the road and look for a small dirt parking area on the right side of the road after three miles. If you pass the small inn, then you’ve gone too far!
The coordinates are 43.9058333333 , -103.446111111 (via mindat.org).
There is very little information found online or in books about the Ingersoll Mine. It’s unfortunate because it has such a fascinating history! I was only able to find one resource about it, an unpublished paper titled “A Mine With More Varieties Than Heinz Does Pickles” by A.I. Johnson. There are no copies available online, so I transcribed it. It can be found here.
Johnson, A.I. “A Mine With More Varieties Than Heinz Has Pickles – The Ingersoll Mine, Keystone, S.D.” March 1983.
Sinclair, K. “Exploring Black Hill’s Hidden Ghost Towns: Ingersoll Mine.” Retrieved from Black Hills Visitor Guide