Open as the Gyfeillon Pit August 1851 by John Calvert [1812-1890], later renamed Great Western Colliery. Hetty Shaft was sunk in 1875 to 392 yards. There were three pits in this colliery Hetty Pit [downcast, later upcast] No No 2 and Pit No 3 [downcast]. On Tuesday,April 11, 1893 there was a fire in the colliery and 63 men and boys died.
The Great Western Colliery continued producing coal for many years after disaster, and the deaths still continued. The Hetty shaft was closed in 1926, but remained as an upcast shaft for the Tymawr Colliery. The No.2 and No.3 shafts. the old Tymawr shaft were closed the same year and a new Tymawr Pit was opened up. In 1928 the colliery came under the ownership of the Powell Dyffryn Coal Co. remained so until the mines were nationalised in 1947. In 1958 the Lewis Merthyr Colliery, a mile or two North-west of the former Great Western Collieries amalgamated with the latter and joined underground, at which time coal winning stopped at the former and materials ceased going down at Tymawr. In 1969 combined collieries were officially named the Tymawr and Lewis Merthyr Colliery. The last dram of coal raised at the Tymawr colliery was on June 21st 1983 and colliery was demolished soon after. Today only the head frame and winding engine house and steam winding engine of the Hetty Pit survive. It was originally intended to be incorporated into the Rhondda Heritage Museum, but its future is now unclear. The Hetty winding house and engine are now being renovated by volunteers under supervision of Mr. Brian Davies of the Pontypridd Museum.
Description from rhychydwr1