{"id":3507,"featured":0,"modified":"2026-04-17 19:58:10","latitude":46.01453809738895728287388919852674007415771484375,"longitude":-112.53143012523651123046875,"title":"Stamp Mills","subtitle":"","fullsize":"https://storyofbutte.org/files/fullsize/6070e0117cead308d2e43bbd7bfeae01.jpg","address":"","all_locations":[],"zoom":18,"creator":["Fred Quivik"],"description":"In addition to a variety of ornamental plantings, the Old Lexington Gardens features a small wooden headframe and two five-stamp batteries. The stamps were used in the old Lexington mill, which sat nearby, where the southeast corner of Broadway and Arizona is now located.<br />\r\n<br />\r\nGenerating a profit from mining requires more steps than simply removing ore from the ground. The ore must be processed to yield a useful product, and the product must be transported to market. The potential products that first attracted miners to Butte were precious metals, gold and silver. To extract the precious metals from ore, the ore first had to be crushed to a sufficiently small particle size for processing. When underground mining began in Butte in the late 1860s, the principal technology for crushing ore was the stamp mill, a name that referred both to the mechanized piece of equipment and to the building that housed the process. A stamp mill was a device that worked like a mortar and pestle. A battery of stamps included an iron or steel mortar box that held the ore as it was being crushed; several stamp stems, each with a cast iron shoe at the bottom, that dropped by gravity onto the ore; a camshaft; and a wooden frame that held the parts of the battery together. Each stem had a tappet at the top making it possible for the camshaft along the top of the battery to lift and drop each stamp in particular sequence. A belt attached to a steam engine turned the camshaft. After the ore was crushed, it could be moved to an amalgamation apparatus in which mercury would combine with the particles of gold and silver to form an amalgam, similar to the amalgam of mercury and gold or silver that dentists once used for fillings. The amalgam could then be removed to a retort (also called a mercury still), which heated the amalgam to a temperature at which the mercury evaporated, leaving molten gold and silver that could be cast into bars of bullion. The mercury vapor was captured and condensed to a liquid to be used again.<br />\r\n<br />\r\nAll Butte’s largest silver mills (Alice, Moulton, Lexington, and Silver Bow) used stamp mills to crush and process their ores, as did the earlier, pioneering mills (Hendrie, Dexter, Centennial, Grove Gulch, and others). Butte’s silver ores were more complex than free-milling ores (meaning ores that could yield precious metal by crushing and simple amalgamation), so the successful mills first had to roast the ore with salt so that the precious metals could be recovered by amalgamation. Charles Hendrie had built what came to be called the Old Lexington Mill in 1868. It was not a success. Andrew Jackson Davis bought Lexington mine in 1876 and acquired and rehabilitated Hendrie’s mill in 1877, making the operation a success. The mill was usually called the Davis mill. He sold the mine and mill to a French syndicate in 1881. That company built a new, larger mill, with apparatus for roasting the ore, just southwest of the Lexington shaft in Walkerville, at which time the Davis mill came often to be called the Old Lexington mill. Without capacity to roast ore, the Old Lexington mill operated only intermittently until 1890, and it was dismantled in 1891. None of Butte’s silver mines survive except the Lexington, in Walkerville, which became a zinc mine after the end of the silver era.<br />\r\n<br />\r\nBy 1879, as Butte was booming as a silver-mining camp, some miners were finding ore that was rich in copper. They, too, had to find a way to process their ore at Butte to earn a profit, but that entailed a differing kind of milling (called concentration) and smelting. Butte became a world-class mining center because of its copper production. Nevertheless, it was silver that led to the major investments of capital that made Butte a booming mining center for copper. <br />\r\n<br />","sponsor":"Superfund Advisory and Redevelopment Trust Authority and The Foundation for Montana History.","accessinfo":"","lede":"Old Lexington Gardens is a recent landscape feature installed on the west side of a rise where the old Washington School was once located, between Broadway and Granite, just east of Arizona Street.","website":"","related_resources":[],"factoids":[],"files":{"https://storyofbutte.org/files/fullsize/6070e0117cead308d2e43bbd7bfeae01.jpg":{"id":5669,"mime-type":"image/jpeg","title":"Stamp mill at the Old Lexington Gardens.","description":"The term “stamp mill” can refer to the machine pictured here as well as to the building that housed the entire process of crushing ore with stamps and then recovering precious metals (gold or silver) using amalgamation with mercury or other means. <br />\r\n | Photo by Fred Quivik.","thumbnail":"https://storyofbutte.org/files/square_thumbnails/6070e0117cead308d2e43bbd7bfeae01.jpg"},"https://storyofbutte.org/files/fullsize/116dd7e247733740674dd2c8b477671e.jpg":{"id":5670,"mime-type":"image/jpeg","title":"Typical 19th-century stamp mill.","description":"The stamp mill on display at the Old Lexington Gardens represents the standard configuration of stamps, mortar box, camshaft, and aprons used throughout the American West at gold and silver mines. It was often called the California stamp mill because the particular details of the configuration developed there in the wake of the California Gold Rush.  | Henry Louis, A Handbook of Gold Milling (New York: The MacMillan Company, 1902), 238.<br />\r\n","thumbnail":"https://storyofbutte.org/files/square_thumbnails/116dd7e247733740674dd2c8b477671e.jpg"},"https://storyofbutte.org/files/fullsize/3a63a9b3ad038cb749bc98f411885d60.jpg":{"id":5671,"mime-type":"image/jpeg","title":"Water-powered stamp mill in Europe in the 1500s.","description":"Stamp mills had been used in Europe for at least 500 years by the time the technology reached Butte. This illustration of a stamp mill appeared in Georgius Agricola’s classic 1556 treatise, De Re Metallica. Agricola (whose name at birth was George Bauer) was a German physician living in Freiberg who studied the metal mines in the region around his city. Written in Latin, his book stood as the leading practical textbook for miners in Europe for almost 200 years. It stands today as a valuable source for the history of mining technologies.  | Georgius Agricola, De Re Metallica, translated from the Latin by Herbert Clark Hoover and Lou Henry Hoover (New York: Dover Publications, Inc., 1950 edition of the original 1912 publication), 284.<br />\r\n<br />\r\n","thumbnail":"https://storyofbutte.org/files/square_thumbnails/3a63a9b3ad038cb749bc98f411885d60.jpg"},"https://storyofbutte.org/files/fullsize/27703e73a96b09a05b7bc1961a790604.jpg":{"id":5672,"mime-type":"image/jpeg","title":"Sanborn Map Showing the Old Lexington Stamp Mill in 1884.","description":"The mill is called “Old” because, by 1884, the French syndicate, which bought the Lexington mine in Walkerville, had built a new 40-stamp mill southwest of the Lexington shaft. The new Lexington mill went into operation in 1882.   | Sanborn Fire Insurance Map for Butte, 1884, sheet 7, Library of Congress Digital Collections.<br />\r\n","thumbnail":"https://storyofbutte.org/files/square_thumbnails/27703e73a96b09a05b7bc1961a790604.jpg"},"https://storyofbutte.org/files/fullsize/f201050a397a3c07ea4e5e3a94edc6b7.jpg":{"id":5673,"mime-type":"image/jpeg","title":"Sanborn Map showing the Alice mills in Walkerville, 1884.","description":"The Alice Gold &amp; Silver Mining Company owned and operated the largest milling works among Butte’s silver-mining companies. The Alice built the mill on the right in 1877. It initially operated with 15 stamps and was enlarged with another five stamps in 1878. The second Alice mill was built in 1880 with 60 stamps. (Note: the Sanborn map states that the two mills had a combined 100 stamps, but this total cannot be documented elsewhere.) Both mills were equipped with roasting furnaces to enhance the company’s ability to recover silver from its complex sulfide ores.   | Sanborn Fire Insurance Map for Butte, 1884, sheet 10, Library of Congress Digital Collections.<br />\r\n","thumbnail":"https://storyofbutte.org/files/square_thumbnails/f201050a397a3c07ea4e5e3a94edc6b7.jpg"},"https://storyofbutte.org/files/fullsize/f76d981eb31d418dc65a67d492d26481.jpg":{"id":5674,"mime-type":"image/jpeg","title":"Walkerville, ca. 1880, showing the Moulton and Alice mines and mills.","description":"This view to the north shows the relatively small settlement of Walkerville, at the top of the Butte Hill, with three large mills on the hill north of Walkerville. W.A. Clark built the 40-stamp Moulton mill (far left) in 1881. The 60-stamp Alice mill, built in 1880, is just to the right of the Moulton mill, while the earlier, 20-stamp Alice mill, built in 1877, is on the right side of the photo. The shaft house of the Moulton mine stands higher on the hill behind the Moulton mill and the 60-stamp Alice mill, while the shaft house of the Alice mine stands higher on the hill behind the 20-stamp Alice mill. Note the long, covered tramway, which links the Alice mine to the 60-stamp Alice mill and was used to move ore from mine to mill (also visible in the Sanborn map).  | Butte-Silver Bow Public Archives, Smithers Collection, photo no. 40.014.1.<br />\r\n<br />\r\n","thumbnail":"https://storyofbutte.org/files/square_thumbnails/f76d981eb31d418dc65a67d492d26481.jpg"}}}