Soudan Underground Mine

Useful Information

Location:	At Soudan. U.S. Highway 169 to Soudan, follow the signs. (47°49'8.73"N, 92°14'34.75"W)
Open:	Underground Mine Tour: Memorial Day Weekend to SEP daily 10-16, on the hour. First three weekends in OCT Sat, Sun 10-16, on the hour. Physics lab tour: Memorial Day Weekend to Labour Day daily 10, 16. Labour Day to SEP daily 12. First three weekends in OCT Sat, Sun 12. [2012]
Fee:	Underground Mine Tour: Adults USD 12, Children (5-12) USD 7, Children (0-4) free (ticket required). High energy physics lab tour: Adults USD 12, Children (5-12) USD 7, Children (0-4) free (ticket required). [2012]
Classification:	Iron Mine, Soudan Iron Formation.
Light:	Incandescent Electric Light System
Dimension:
Guided tours:	Underground Mine Tour: D=90 min. High energy physics lab tour: D=75 min.
Photography:
Accessibility:
Bibliography:
Address:	Soudan Underground Mine, 1379 Stuntz Bay Road, Soudan, MN 55782, Tel: +1-218-753-2245. E-mail: Special in-depth tours, guided by physicists, Eileen Amos, Tel: +1-218-753-6611.
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then. Please check rates and details directly with the companies in question if you need more recent info.

History

1880	an area of 8,000 ha of iron-rich land purchased by Charlemagne Tower.
1884	mine opened by the Minnesota Iron Company.
1901	Ownership passed to the Oliver Iron Mining Division of U.S. Steel Corporation.
1962	mine closed because of technological progress and a changing economy.
1962	opened as a show mine.
1965	site donated to the state by United States Steel Corp.
13-NOV-1966	listed on the National Register of Historic Sites (NRHS).
1989-2001	Soudan 2 Proton Decay experiment.
2004	expected start of MINOS.
2011	mine closed for tours because of fire in shaft.
JUN-2012	reopened.

Geology

Soudan Underground Mine was operated to mine the famous Soudan Iron Formation. This is part of the Iron Range.

The Soudan Iron Formation is a Banded Iron Formation (BIF), an originally sedimentary rock which include layers of hematite. The rock is carbon rich, but because of its age of more than 2.7 Billion years the components are mostly metamorphic. This is called metasedimentary, as the sedimentary layers are still visible. The typical bands are hematite, jasper, and chert. The bands are heavily folded, outcrops of the formation are polished by glaciers which covered the area during the Ice Ages and show a nice pattern.

The Banded Iron Formations are part of the Animikie Group which was deposited between 2.5 and 1.8 Billion years ago in the Animikie Basin. It covers the area form south central Minnesota to Thuder Bay in Ontario, Canada. It is divided geographically into four ranges, Gunflint Range, the Mesabi Range, Vermilion Range, and Cuyuna Range. The Soudan formation is located in the Vermillion Range.

The hematite has an enormous amount of iron (~65%), which makes it a very valuable ore. On the other hand it is mixed with layers of other rocks, so it is necessary to preprocess the ore, to remove the jasper and chert. Also the formation has a vertical orientation, which made underground mining necessary after only a few years of open cast mining. Underground mining is more expensive than open cast, so from the 1960s the rentability of the mine vanished with sinking world market prices for iron.

Description

Soudan Underground Mine is located in Vermilion Range and is the oldest and deepest iron mine in Minnesota. During its 80 years of operation about 15.5 million tons of ore were removed. The mining started in seven open pits. But after some time the mine suffered frequent accidents from falling rocks. To avoid that the operations were moved underground in the 1890s. Technological progress and a changing economy made the mining unprofitable and so all operations ended in 1962.

The Historic Underground Mine Tour shows the last level that the miners worked. The visitors get helmets and then journey down 730 m in an elevator called "the cage". The tour continues with a ride on a rail car on the 27th level. This mining tour is completed by several related buildings on the surface, the dry house (1925), drill shop (1917), crusher house (1904) and engine house (1901).

A second tour concentrates on the High Energy Physics Lab at the bottom of the mine. This lab was built about 800 m deep under the mine after the mining ended. This cavern is not a former part of the mine, but was built using modern underground mining methods right for this purpose. The enormous layer of rocks and iron ore filters most of the cosmic rays, allowing to conduct sensitive experiments which are impossible on the surface. The lab operated the Soudan 2 Proton Decay experiment from 1989-2001, with the goal to observe the decay of a proton. This goal was not achieved, but much valuable data was collected, leading to the MINOS experiment. MINOS stands for Main Injector Neutrino Oscillation Search, the attempt to measure the mass of particles called neutrinos, which are smaller than the nuclei of atoms. A third big experiment at the lab is Cryogenic Dark Matter Search (CMDS), the direct detection of dark matter particles other than neutrinos. While Proton Decay is stopped, the two other experiments are under construction now.