The Middlesex mine (No. 14, pl. 30) lies at the south end of the small valley locally known as Horseshoe Gulch, half a mile southeast of the Yellow Pine mine and 3 miles northwest of Goodsprings, in the Goodsprings Mining District, in Clark County. The mine was located in 1901. There are two tunnels, an upper 100 feet long, and a lower about 400 feet long. The production of this mine is unknown.