Rocky Mountain Concentrator /
A. M. P. Mill
Located in Black Hawk just north of the turntable and water tank.
Mile Post 35.75
The Rocky Mountain Concentrator
Contributed by Keith Pashina
Black Hawk was the city of mills. Spread out up and down Clear Creek, 16 mills were located next to the tramway. Downstream of the main part of town was the Rocky Mountain Concentrator, an ore concentration facility that was served for many years by the Gilpin Tramway Company. The Rocky Mountain Concentrator was unique among the Black Hawk mills, as it was specifically designed for concentration of mill dirt, as compared to stamp mills that broke down and concentrated the ore. The concentrator was used when a more specialized ore treatment was required, to take lower grade ores and process them into a more concentrated form that was economical to send to the smelter for final processing.
The Rocky Mountain Concentrator, or A.M.P. Concentrator (for Associated Mineral Producers) was served by the Gilpin Tramway Company by a spur branching off the three-rail Colorado Central and Gilpin Tramway tracks at milepost 35.78. The mill was located about midway between the New York Mill and the Iron City Mill. To serve the mill, the 2’ gauge track swung briefly up Dory Hill gulch, then used a short switchback to enter the rear of the mill.
Shippers over the years included the Aduddell, Barnes, Dallas and Old Town mines. The surviving traffic records show there was a lot less traffic to this mill than say, the Iron City or Polar Star mills, but never less, there were busy periods. For example, in one month in 1907 the Aduddell shipped 26 ore cars to this mill.
The concentrator was a squat, barn-like building, clad with flat metal siding. Inside the mill was a variety of equipment. This equipment changed over the years, just as the ore bodies mined by the mines changed. In 1899, the annual publication Precious Metals in the United States described the mill as having a 25 stamp capacity, and with rolls and Huntington mills to process the ore, for a daily capacity of 75 tons. The Mining Investor, a biweekly publication, wrote on September 4, 1905, that “on account of increased receipts of custom ores the Rocky Mountain concentrator at Black Hawk has been working three eight-hour shifts and is now running to its full capacity – 100 tons per day.” The same correspondent went on to write, “Manager E.C. Moulton has made several improvements which have produced better results, including the Moulton crusher and tables, and the mill has all the ore that it can handle.” A later report from 1916 stated the mill was closed at that time, but intended to reopen after a new process was installed.
This page was last updated 01/27/07
Copyright 2007 by Mark Baldwin