Missoula’ own quartzites and argillites lack the physical characteristics that could have made them usable in formal building facades. Throughout the United States granite and sandstone proved to be the most versatile and desirable building stone, and Missoula builders would certainly have exploited these varieties had they cropped out around Missoula. Northern Pacific routes had connected Missoula with the outside world in 1883, and by the late 1880’s, Missoula builders actively sought building stone from outside of Missoula for their new crop of buildings.
The Boulder Batholith, an oblong granite body stretching 96 km (60 mi) from Helena, on the north, to Silver Star on the south, hosted dozens of quarries through the years. Stone contractors who developed quarries along the railroads sought an export market and happily supplied the dimension stone needs of Missoula.
The Ten Mile granite quarries, located about 16 km (10 mi) west of Helena, supplied most of Missoula’s dimension stone demands during the building boom of the late 1880s. Missoula businessmen opened a small granite quarry north of Clinton in an attempt to supply Missoula’s granite needs, but the Ten Mile quarries simply out-competed their efforts. The Welch quarry, on Homestake Pass, and the Kain quarries, near Clancy, also shipped building granite to Missoula. The craftsmen commonly shaped the granite at the quarries, shipping only the finished building stone to Missoula; therefore, Missoula never hosted the large numbers of stone craftsmen found around the batholith, at Helena or at Butte.
In 1899, the Montana Sandstone Co. opened its quarry along the Northern Pacific Railroad, near Columbus, and Missoula became one of its key customers. The company shipped cut, blue-gray sandstone to most of the Montana towns along that railroad. Missoula builders, lacking a local sandstone source, imported the Columbus sandstone between 1900 and 1913, for use as for ornament and trim, in more than 100 commercial and residential buildings.
Builders employed minimal stone in Missoula buildings between 1925 and 1950. When construction surged again in Missoula, during the 1950’s, builders again sought sandstone for building facades. Montana Stone Co. opened a sandstone quarry near Monarch and began shipping much of its orangish-tan-colored stone to Missoula. Quarrymen extracted broad sandstone slabs and subdivided these into square blocks with a machine called a ‘hydraulic splitter.” Masons set those square blocks mostly as random ashlar, but also set the irregular slabs as flagging (with the sedimentary bedding planes oriented perpendicular to the ground). A similar sandstone quarrying operation at the Fishtrap quarries, north of Thompson Falls, shipped smaller quantities of buff-colored and maroon-colored building stone to Missoula.
Missoula builders employed a yellow to maroon-colored volcanic ash in a few 1970’s buildings, but its popularity was short-lived. As quarried near Niarada, the stone proved too gaudy for commercial success.
Livingston Marble and Granite Co. currently quarries travertine near Gardiner and shipped much rubble and ashlar to Missoula during the 1950s and 1960s. Quarry crews extract large blocks which the company gang-saws and splits at its Livingston plant. As of this writing, the company operates one of the few successful building stone quarries in Montana.
Several small-scale quarries also continue to operate in the Plains-Paradise area. These quarries produce a flaggy, dark gray argillite which resembles slate. This Pritchard Formation argillite, dated at around one billion years, ranks as one of Montana’s most ancient building stone varieties. Stone masons began setting the stone as flagging in the 1970’s and continue this practice today.