The Floresta Mine was located 11 miles mostly west of the mining town of Crested Butte. A narrow gauge branch of the Denver & Rio Grande Railroad served the Floresta mine. Floresta was known as "the highest coal mine in the world," operating at an altitude of over 10,000 feet.
The land that the Floresta Coal Mine stood on was first claimed by W.V. VanOstern, who represented the Osage Coal and Mining Company in 1879. Development on the land didn't occur for several years due to the fact that at the time, the nearest railroad point was 150 miles away and the market was very limited. Later, the land changed hands from the Osage Coal and Mining Company to four people; The Thatcher Brothers, and two other men by the names of Thompson and Reynolds. The opened the Ruby mine and used it to supply coal to the gold miners at the town of Irwin until it (either the town or the Ruby Mine) was abandoned. President J.A. Kebler of the Colorado Fuel Company bought the property and it was then integrated into the Colorado Fuel and Iron Company's holdings in the merger of 1892.
The coal mined at the Floresta Coal Mine was a type of anthracite. Anthracite coal has the highest percentage of carbon of all coal types and was the most desired for heat in domestic settings due to its clean burning nature and low smoke production. Mining operations began in October of 1893 with a drift entry according to (Jackson?). Other CF&I records indicate, however, that mining of Floresta began in 1896. and 1919 was the last production year. Floresta was first mined on the east side of the canyon where the breaker was built, but closed in 1899 due to the thinness of the vein. Mining on the west side, meanwhile, started in 1897 with the opening of four entries in coal that had a more regular thickness.
Coal was hauled with the use of mules to a balanced hoisting system that took the cars to the surface and then dropped the empty cars back down into the mine. From there, the coal went down a 1,400-foot inclined plane to the tipple where there were two sets of rolls and five revolving screens. The coal was then loaded into the narrow gauge railroad cars for shipment. when in operation, around 100 men were employed, who were able to produce 300 tons of coal per day. This was hindered by the closing of the camp in the winter due to snow and the lack of amenities of the camp.
The mine closed permanently in December 1920. Floresta operated at most six months of each year because of the winter weather conditions; which also hindered the railroad's ability to bring cars up to the mine. The demand of coal was always higher than what the mine could produce and shipments were made as far away as Montana and California.