Between 1920 and 1940, the older companies mining the central shallow area ceased operations, leaving only  North, South , Zinc and NBHC Mines at the ends of the lode.  The South Mine closed in 1972 and its leases were acquired by Minerals, Mining and Metallurgy (MMM).  MMM removed low – grade remnant ore from the  central portion of the orebody by open – cut method between 1976 and 1991.  NBHC and Zinc Mines (both owned by Australian Mining and smelting LTD, a subsidary of CRA) consolidated to form ZC Mines in 1986 which subsequently merged with North Broken Hill Ltd to form Pasminco Ltd in 1988. North Mine closed in 1993 leaving one mine in Broken Hill,  Pasminco,  which is closing down in the year 2006.                                                               BHP MINE The seven mining leases pegged by the syndicate of seven in 1883 were almagated in 1885 to form BHP and, by 1888, the company retained only blocks 11, 12 and 13 along the crest of the outcropping lode.  Initially, a series of shafts were sunk into the rich ore and substantial profits were earned.  During its first three years, BHP produced 7 million ounces of silver, about one – third of world production. The first smelting furnaces were installed by BHP in 1886 (the north smelters) and a second complex (the south smelters) was added in 1888. Eventually 15 furnaces with  a total capacity of 4,5oo tons of ore per week were built.  The BHP Mine dominated  Broken Hill during its early years and paid more than I million pounds in dividends by the early 1890s.  It was known locally as the Proprietary, the Prop or just the Big Mine. Open cutting of the hill commenced in 1891 and, in 1894, a concentration mill with a capacity of 1,500 tons per week was erected.  Another mill, with a capacity of 10,000 tons per week, was erected in 1897 using part of the south smelter slag dump.  The stone foundation of the second mill survives today near Delprat Shaft. The mine was at its peak between 1900 and 1908, when up to 13,000 tons of ore were extracted per week.  Employing nearly 3,500 men or more than one – third of the entire mine workforce, the Big Mine clearly ruled the line of lode. However, the mine’s richest ore was exhausted by 1908 and the company began to look elsewhere for profit.  The wealth won at Broken Hill by BHP Mine finally closed in 1939, having made 30 million pounds profit from 12.3 million tons of ore worth 54 million pounds.  Today BHP is known as the Big Australian. The mine was reworked by Broken Hill South LTD between 1951 and 1961.                                                      BLOCK 10 MINE Block 10 was one of the original BHP leases, which was floated as a separate company in 1888 as the BHP Block 10 Co. LTD.  A concentration mill was erected at the mine in the 1890s to treat sulphide ore.  Underground subsidence seriously affected the mill and, as a result, a new mill was erected on the adjacent hill in 1903. An aerial ropeway, the first at Broken Hill, was completed in 1904 and transported broken  ore 600 metres from the mine to a large storage bin above the concentration mill, which could treat 3,500 tons of ore per week. Production totalled  2.5 million tons of ore worth 5 million pounds and dividends of 1.5millions pounds were paid up to 1923 when the mine and mill closed and were purchased by BHP. The mine was reworked by Broken Hill South LTD between 1946 and 1960, and much of the mine site is now covered by overburden dumps from modern open – cut operations.                                                    BLOCK 14 MINE Block 14 was also one of the original BHP leases and was floated as a separate company in 1887.  The mine, like others on the centre of the lode, was noted for its rich oxidised ore.  A smelting works was erected on the site in 1889 but closed in 1894 when smelting works commenced at Port Adelaide.