Milfraen Colliery was opened in 1865 and was operated by John Jayne until it was taken over by the Blaenavon Iron & Steel Co in 1884. Later linked to Garn Pits and Kays Slope, coal was last raised in 1933, after which the shaft was used for ventilation purposes only. The private railway is on the S side of the Blaenavon branch of the LNWR, opened in 1869. The colliery line may be contemporary with the LNWR. The junction was known as Jayne's Branch Junction, after the colliery owner, who was also a director of the Brynmawr & Blaenavon Railway Co, which became vested in the LNWR in 1869.
A single track railway S of the LNWR (nprn 67497), curves round to the W in a cutting, then on an embankment where it curves sharply to the E. From this point it is laid with tarmac and is part of a private road to Blaentillery Mine. The original railway continued 400m SE of the colliery, ending at approximately SO222 097.
