The arrival at Broken Hill from Melbourne on 2 April 1905 of a group of 20 financiers, mining experts, directors and shareholders heralded a new phase in the Broken Hill mining industry. The main objective of the influential party which included W.L. Baillieu, and brothers Lionel and William Sydney ('W.S.') Robinson was to assess the potential treatment and the marketing of the resultant products of six million tonnes of sand and slime residue dumps which had been deposited on the various mine leases during the preceding 20 years. The value of the minerals, principally zinc, contained in the surface deposits locally referred to as 'skimp' dumps was estimated at $12 million.

Arising out of the visit, and subsequent inspection by Herbert C. Hoover, 'a young mining engineer who subsequently became President of the United States of America, The Zinc Corporation Limited was formed in Melbourne on 9 September 1905.

The new company established a concentrating mill, initially on a British mine lease, and in 1910 on a lease held by the South Blocks company, to treat dump material purchased from existing mines. (Also in 1905, Amalgamated Zinc (De Bavay's) Limited was formed to treat dumps purchased from the North, South, British, Block 14 and Block 10 mines. A plant was erected on a North mine lease, and operated until 1924. The De Bavay company was instrumental in establishing the Electrolytic Zinc Company of Australia Limited in Tasmania, to convert Broken Hill zinc concentrate into zinc bullion. An earlier Organisation Australian Metal Company Limited, had purchased residues and established a zinc treatment plant in Rakow Street in 1899. The venture was unsuccessful, the plant and buildings being dismantled in 1910.)

The Zinc Corporation Limited acquired the South Blocks company in 1911 and began developing underground operations on the leases, in addition to the treatment of dump material.' The transition of the Zinc company from its primary role of treating surface residues, to the mining of ore, was largely brought about by William Clark & Co., W.L. Baillicu, Lionel C. Robinson, W.S. Robinson and Francis A. Govett.

In 1936 Broken Hill-born A.J. Keast returned from Canada to take up the position of general manager of The Zinc Corporation Limited. Under his vigorous and imaginative leadership a complete reconstruction of the company's operations took place, particularly on the surface where imposing new buildings were erected, and lawns, gardens and plantations were established.

Also in 1936 the Zinc company was responsible for the formation of a new organisation, New Broken Hill Consolidated Limited. Work on the NBHC leases was intensified immediately after World War 11, under the management of The Zinc Corporation Limited. In the post-war years, through a series of amalgamations and mergers, the original Zinc company became a subsidiary of Conzinc Riotinto Australia Limited (CRA Limited from I August 1980), controlled by the giant, London-based Riotinto Zinc Corporation Limited (RTZ).

The names of W.S. Robinson and his son, Lyefl, are permanently associated with the post-war development, and world-wide expansion of The Zinc Corporation Limited. So, too, is Maurice Mawby, who was born at Broken Hill and distinguished himself in the fields of geology and metallurgy before being appointed to managerial positions with the Zinc, and NBHC companies. He was knighted in 1963 for his services to the mining industry, and died in 1977 at the age of 73.

The Zinc Corporation Limited and New Broken Hill Consolidated Limited continue to operate under joint management at Broken Hill, where their combined production of lead-silver-zinc ore approximates 80% of all ore produced at Broken Hill each year.

At the northern, southern and western boundaries of the principal mines, a number of syndicates and companies pegged claims and sank shafts in hopeful anticipation of intersecting the main orebody. To the north were the Silver Crescent, Imperial, Cosgrove, Round Hill, Consolidated, Globe, Carbonate Ridge, Potosi, Silver Hill and Silver Peak mines. Eastwards were the Bonanza and the Consols companies, while to the south were the Rising Sun and White Leads claims. In addition, the Brisbane Blocks (later Broken Hill Blocks) company held two leases immediately west of the BHP mine, between the latter and Crystal Street, and carried out diamond drilling operations without success. The Broken Hill Extended mine adjoined the southern boundary of Block 10, west of Block 8 (South Mine).

From some claims a limited quantity of upper level ore was obtained. As it transpired, only the principal 'line of lode' mines were to extract ore from the original massive deposit. The Consols mine provided an unusual mixture of minerals, and in 1891 produced the Turtle slug of almost pure silver, weighing 813 kg.

The standard of management of several of the smaller mines is typified in an extract from a description of the Silver Crescent mine, which appeared in the Barrier Miner on 4 July 1889: The shaft, which is down about 170 feet, is a disgrace to an ordinary prospector, and I cannot conceive why such a monstrosity has been allowed to pass the notice of any board of directors possessed of a modicum of brains. When at the bottom it is a treat to look upwards and try to see the sky. The wretched nature of the work is thus fully exposed to the observer, as it looks as if a clumsy attempt has been made to hew out a sort of spiral staircase.

With geological hindsight, it is now known that the early mines of the Barrier, which operated at a distance of several kilometres from the Broken Hill deposit, obtained ore from a much younger, thinly dispersed orebody, named the Thackaringa Lode, estimated to have been laid down about 500 million years ago. Of the mines in the Thackaringa, Purnarnoota, Day Dream, Umberumberka and other outlying areas, only the Pinnacles survived, being operated by various companies and syndicates on a spasmodic basis, until its final closure in 1971.

Over the years millions of dollars have been expended by the Broken Hill mining companies in search for new orebodies in the Barrier Ranges, and for a possible extension of the original deposit. Since the first lease was pegged over the original Broken Hill orebody in 1883, and with the possible exception of the rich ore located 1.6 km below ground level by North Broken Hill limited in 1975, no new deposits have been discovered during that time. NBHC and Zinc Mines (both owned by Australian Mining and Smelting Ltd, a subsidiary of CRA) consolidated to form ZC Mines in 1986 which subsequently merged with North Broken Hill Ltd to form Pasminco Ltd in 1988.