Drift mining

These are simply tunnels made in the rock, with a size and shape depending on their use—for example, haulage, ventilation, or exploration.

[5] The Boulder-Weld Coal Field beneath Marshall Mesa in Boulder, Colorado was drift mined from 1863 to 1939.

Too small for commercial operation, the mine probably provided coal for the Lusk family and later for the park.

[9] In 1820 the first commercial mine in Kentucky, known as the "McLean drift bank" opened near the Green River and Paradise in Muhlenberg County.

The first ton of coal in a shaft mine 100 feet in depth and having a daily capacity of 600 tons frequently costs the mining adventurer upwards of $20,000 (1888), and cases are on record where owing to the extraordinary amount of water in sinking, $100,000 (1888) have been expended before coal was reached.

Water is, however, an expensive item in drift mines opened on the dip slope of the coal, and underground hauling under such conditions is unusually costly.

[16] Many, many references to and photographs of WV drift mines in the Scrapbook of Appalachian Coal Towns,[17] including Sprague, Kaymoor, Nuttallburg, Venus, Layland, Elverton, Casselman (aka Castleman), etc.

Many miners tunneled into deep placer deposits, bringing out the high-grade gravels to be washed at the spring thaw.

Gold was usually found on top of "false bedrock," a layer of clay that occurred at the base of the beach or stream deposit.

Miners initially sank shafts to prospect for the pay streaks by building a fire atop the permafrost, then as it melted, shoveling away the mud.

Hydraulic mines, using powerful water cannons to wash whole hillsides, were the chief sources of gold for the next 20 years.

[18] Drift mines in eastern Kentucky are subject to roof collapse due to hillseams, especially within 100 feet of the portal.

Hillseam is the eastern Kentucky miners term for weather-enlarged tension joints that occur in shallow mine overburden where surface slopes are steep.

They can intersect at various angles, especially under the nose of a ridge, and create massive blocks or wedges of roof prone to failure.