Complex sentence: The history of the mining sector of the country is ancient, traced to the iron ore mine of the western Ngwenya mountains, which has since 1975 been closed; it is said to be the oldest iron ore mine in the world.
Split into simpler sentences: The history of the mining sector of the country is ancient, traced to the iron ore mine of the western Ngwenya mountains, which has since 1975 been closed. Ngwenya Mine is said to be the oldest iron ore mine in the world.