director) and RM Preston (commercial director), as well as other executives involved with technical and other matters. Perhaps most significant was the company's investment in copper mines in Northern Rhodesia, later Zambia, which it eventually consolidated into the Rhokana Corporation. These and later efforts at diversification eventually allowed the company to divest from the Rio Tinto mine in Spain. By the 1950s, Franco's nationalistic government had made it increasingly difficult to exploit Spanish resources for the profit of foreigners. Rio Tinto Company, supported by its international investments, was able to divest two-thirds of its Spanish operations in 1954 and the remainder over the following years. Major mergers and acquisitions Like many major mining companies, Rio Tinto has historically grown through a series of mergers and acquisitions. Early acquisitions The company's first major acquisition occurred in 1929, when the company issued stock for the purpose of raising 2.5 million pounds to invest in Northern Rhodesian copper mining companies, which was fully invested by the end of 1930. The Rio Tinto company consolidated its holdings of these various firms under the Rhokana Corporation by forcing the various companies to merge. Rio Tinto's investment in Rhodesian copper mines did much to support the company through troubled times at its Spanish Rio Tinto operations spanning the Spanish Civil War, World War II and Franco's nationalistic policies. In the 1950s, the political situation made it increasingly difficult for mostly British and French owners to extract profits from Spanish operations, and the company decided to dispose of the mines from which it took its name. Thus, in 1954, Rio Tinto Company sold two-thirds of its stake in the Rio Tinto mines, disposing of the rest over the following years. The sale of the mines financed extensive exploration activities over the following decade. Merger with Consolidated Zinc The company's exploration activities presented the company with an abundance of opportunities, but it lacked sufficient capital and operating revenue to exploit those opportunities. This situation precipitated the next, and perhaps most significant, merger in the company's history. In 1962, Rio Tinto Company merged with the Australian firm Consolidated Zinc to form the Rio Tinto – Zinc Corporation (RTZ) and its main subsidiary, Conzinc Riotinto of Australia (CRA). The merger provided Rio Tinto the ability to exploit its new-found opportunities, and gave Consolidated Zinc a much larger asset base. RTZ and CRA were separately managed and operated, with CRA focusing