Primary traffic on the railway has always been mineral, first with nitrate (an essential ingredient of explosives prior to World War I) and as of 2020 copper being very important. Sulphuric acid is transported uphill and copper comes down.
Mineral traffic on the railway has consistently included both nitrate (a vital ingredient for explosives prior to World War I) and, by 2020, copper, which is now very important. Sulphuric acid moves uphill while copper travels downhill.