Drift mining
A horizontal tunnel cuts into the side of a hill in 1968. Paul W. Thrush wrote this definition for the US Bureau of Mines. He described drift mining as working coal seams accessed by adits driven directly into the surface outcrop. This method differs from shafts that go straight down or crosscuts that slice across veins. A drift follows the bed of ore rather than intersecting it at an angle. These passages serve multiple purposes like haulage, ventilation, or exploration. They remain near-horizontal and generally stay above water levels within the mountain.
Early miners dug exposed coal on the surface before following seams underground in the British Isles. Records show coal digging occurred in Durham, Northumberland, Nottinghamshire, Derbyshire, Staffordshire, Lancashire, Gloucestershire, Lothian, and Wales during the 13th century. By the 20th century, drift mines still operated in Derbyshire, Yorkshire, Cumbria, and Wales. The largest operating mine became Aberpergwm, located in South Wales. Historical records span from the first series published to 1835 through the second series covering 1835 to 1880. Reprints appeared in 1971 to preserve these early industrial accounts.
The Boulder-Weld Coal Field beneath Marshall Mesa in Colorado was drift mined from 1863 until 1939. Measurements taken in 2003, 2005, and 2022 revealed an active coal-seam fire there. This fire was investigated as a possible cause of the 2021 Marshall Fire. In Illinois, Argyle Lake State Park sits over rich coal, clay, and limestone resources since 1948. Individuals commonly dug their own drift mines to supplement income at Argyle Hollow. Small operations known as country bank or farmer mines produced limited quantities for local use across Appalachia. The Lusk Mine operated from the late 1800s through the late 1920s inside Turkey Run State Park. It likely provided coal for the Lusk family before serving the park itself. The McLean drift bank opened near Green River and Paradise in Muhlenberg County, Kentucky, in 1820. Beaver Coal & Mining Company became the most well-known operator in Drift, Kentucky. Other smaller mines included Floyd-Elkhorn Consolidated Collieries and Turner-Elkhorn Coal Company. Graff Drift Mines existed near Blairsville in Indiana County while Empire F Mine ran from 1910 onward. Rodkey Mine operated in Clymer starting in 1906. Ernest Mine No. 2 functioned from 1903 until 1965 in Rayne Township. A photo by Lewis Hine captured a drift mine entry in West Virginia during 1908.
Drift mining methods were used extensively to mine placer deposits during the early years of the Nome mining district starting in 1899. Surface deposits could be worked during summer but some lay too deep for surface placering. Water to wash gold from placers was not available in winter months. Miners tunneled into deep placer deposits bringing out high-grade gravels to be washed at spring thaw. Most ground in Nome consists of permafrost. By drift mining miners recovered much gold buried under the frozen layer. Gold concentrated in three ancient beach lines now sit above sea level. These lines lie buried under roughly fifty feet of permafrost overlain by two feet of tundra. Miners initially sank shafts to prospect for pay streaks by building fires atop the permafrost. As it melted they shoveled away mud down to either a pay streak or bedrock. When gold was found drift mining began with horizontal tunnels following the gold along bedrock surfaces. The tunnels did not cave in because the ground remained frozen. Around 1900 the population of Nome exceeded twenty thousand people, many working as drift miners. Today's miners sometimes hit old drifts using modern drilling equipment copied from Welsh coal miners.
Gold mined from placer deposits up and down California existed in varied environments until about 1864. Hydraulic mines using powerful water cannons became chief sources of gold for the next 20 years. Judge Lorenzo Sawyer issued a decree in 1884 prohibiting dumping hydraulic mining debris into the Sacramento River. This effectively eliminated large-scale hydraulic operations across the state. For the next 14 years drift mining partially made up for lost production in buried Tertiary channels. Overall production declined during this period before rising again with large-scale dredging. The first successful gold dredge appeared on lower Feather River near Oroville in 1898. Michael Silva documented these methods for the California Department of Conservation Division of Mines and Geology in 1986.
Drift mines in eastern Kentucky face roof collapse due to hillseams within 100 feet of the portal. The US Bureau of Mines published a study of eastern Kentucky drift mines in 1989. Hillseams were identified as dominant geologic causes of roof instability unique to outcrop barrier zones. Many roof fall injuries and fatalities attributed to them occurred in shallow mine overburden where surface slopes are steep. Hillseam is the term miners use for weather-enlarged tension joints occurring under 300 feet or less of overburden. These features form by stress relief and tend to parallel topographic contours and ridges. They can intersect at various angles especially under nose of a ridge creating massive blocks prone to failure. Gary Sames and Noel Moebs described examples of hillseams in both outcrop and coal mine roofs to establish their geologic character.
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Common questions
What is drift mining and how does it work?
Drift mining involves working coal seams accessed by adits driven directly into the surface outcrop. This method follows the bed of ore rather than intersecting it at an angle like shafts or crosscuts do.
When did early miners start digging exposed coal in the British Isles?
Records show coal digging occurred in Durham, Northumberland, Nottinghamshire, Derbyshire, Staffordshire, Lancashire, Gloucestershire, Lothian, and Wales during the 13th century. By the 20th century, drift mines still operated in Derbyshire, Yorkshire, Cumbria, and Wales.
Where was the Boulder-Weld Coal Field located and when was it mined?
The Boulder-Weld Coal Field beneath Marshall Mesa in Colorado was drift mined from 1863 until 1939. Measurements taken in 2003, 2005, and 2022 revealed an active coal-seam fire there that was investigated as a possible cause of the 2021 Marshall Fire.
How did drift mining methods help recover gold in the Nome mining district starting in 1899?
Miners tunneled into deep placer deposits bringing out high-grade gravels to be washed at spring thaw because water to wash gold from placers was not available in winter months. Most ground in Nome consists of permafrost so miners recovered much gold buried under the frozen layer by following horizontal tunnels along bedrock surfaces.
Why do drift mines in eastern Kentucky face roof collapse issues?
Drift mines in eastern Kentucky face roof collapse due to hillseams within 100 feet of the portal. Hillseams are weather-enlarged tension joints occurring under 300 feet or less of overburden that form by stress relief and tend to parallel topographic contours and ridges.