John Ewing was born probably on 3 November 1844 in Bonhill, Dunbartonshire, Scotland, the son of Ann Barclay and Archibald Orr Ewing, a manufacturer. Little is known about Ewing's early life other than that he was educated at the local academy. He arrived in Otago, New Zealand, in 1863, mining at Gabriels Gully and Fourteen Mile Beach before joining the rush to the Dunstan Creek goldfield (St Bathans) in February 1864 and settling there to embark on a long career as a mining entrepreneur.
As a member of a partnership Ewing worked a claim on Surface Hill, displaying considerable ingenuity in mining this difficult terrain. He was an original shareholder, and later director and chairman, of the Scandinavian Water Race Company which, together with the Enterprise and Mountain water race companies, supplied most of the water to the St Bathans miners. Ewing was still at Surface Hill when on 26 November 1871 he shot a Chinese miner, Ah Cheow. This was a serious incident at a time of rising racial tension and scurrilous denunciations of Chinese miners for their alleged pilfering. Convicted by a reluctant jury on a charge of causing grievous bodily harm, Ewing was sentenced in July 1872 to a term of 18 months' imprisonment, with Ah Cheow having to serve three months for theft of gold from Ewing's claim. Strong public pressure saw Ewing released after just four months.
Returning to St Bathans, Ewing in 1873 purchased a small claim on Kildare Hill, ground originally opened in 1864 by a party of miners from County Kildare, Ireland. Installing modern mining appliances, including a Little Giant monitor in 1876 and hydraulic elevators in 1886, Ewing secured rich returns. He was a foundation shareholder, and later director and manager, of the St Bathans Channel Company, formed to construct a tailings channel to permit the working of the deep Kildare Hill claim. By 1894 he was working 100 feet below the level of his tailrace, and in that year modified and installed an elevator designed to raise the wash in one lift. On 15 November 1894, to the discomfort of the sceptics assembled, the elevator operated perfectly, 'a spontaneous cheer' bursting forth 'when it was seen that science, combined with practice, had prevailed over theory.'
During the 1870s Ewing actively advanced the interests of his fellow miners. He contributed to the formation of the St Bathans District Miners' Association (1873), and the Otago Central Mining Association (1874), serving as president from 1874 to 1876, and was the St Bathans delegate to the Otago Mining Conference held at Clyde in 1874. Throughout, he pressed for the abolition of the gold duty, reduction of goldfields taxation, the resolution of the riparian rights conflict which in 1874 threatened to paralyse alluvial mining, and the protection of miners' interests with respect to land settlement. It was largely on these issues that in 1874 he contested the vacant Otago Provincial Council seat of Mount Ida, but attracted little support beyond that of his fellow miners. In 1881 as a member of Vincent Pyke's Otago Central Land League he made clear miners' disquiet over the league's campaign and presented evidence to the Otago Pastoral Leases Committee proposing various measures intended to preclude conflict between miner and settler. In St Bathans itself, Ewing contributed to various organisations: the school and hospital committees, sports clubs, the Hope of St Bathans (a district lodge of the Good Templars), and served almost 20 years as a Maniototo county councillor, including terms as chairman from 1879 to 1881 and in 1887. On 24 May 1883, at St Bathans, Ewing married Mary Frances Bunny (formerly Kelly), widow of the local post and telegraph master F. J. Bunny. There were to be no children.
Rich returns from his Kildare Hill mine encouraged Ewing to invest and develop other mining ventures. In 1881 he established an extensive mining settlement on Vinegar Hill, near St Bathans, later extending it to nearby Shepherds Flat. In partnership with St Bathans storekeeper William McConnochie he invested £10,000 in constructing a water race at Matakanui in 1888; the pair purchased the property of the Hercules No. 2 Gold-mining Company at Roxburgh in 1892, and in 1897 that of the United Hercules Hydraulic Sluicing Company. He made further investments at Welshman's Gully, Cambrian, in 1893, and at Bald Hill Flat (Fruitlands), where in 1896 he purchased the property of the defunct Bald Hill Sluicing Company. In all his enterprises he invested heavily in applying the continuous use of modern, efficient plant to treat large quantities of low-grade ground. He also invested in land, purchasing 1,570 acres in the St Bathans area between 1883 and 1891; this land was sold in March 1900.
Continuing to enjoy the respect of his fellow miners, in 1884 Ewing fought Scobie Mackenzie for the Mount Ida electorate. Describing himself as a liberal, Ewing advocated the speedy construction of the Otago Central railway, land nationalisation, suspension of immigration during recessions, state aid to Catholic schools, and the conservation of miners' various interests. Ewing was no match for Mackenzie's wit and eloquence, and was the subject of acrimonious criticism, not least that while he had 'a dead-set on the squatters' for their monopolising of the purchase and leasing of land, he himself had engaged in similar practices at the expense of his fellow miners. He was affected too by recollections of the 1871 shooting incident. Ewing was also to lose to independent Liberal A. L. Herdman in 1902. He was never able to appeal to more than narrow sectional and district interests.
Although he enjoyed some major mining successes, by the late 1890s Ewing was in growing financial difficulties: his mining operations were plagued by recurring water shortages, slips in the claims, exhaustion of auriferous ground, declining returns, and at Kildare Hill where work ceased in 1900, insufficient fall to carry off accumulated tailings. In 1903 the Scandinavian Water Race Company initiated a protracted legal battle against Ewing which saw him lose his Kildare property until the Court of Appeal, to which he skilfully presented evidence, in 1906 reversed the decisions of the lower courts. Following Ewing's declaration as a bankrupt in September 1905, however, the Scandinavian Water Race Company purchased the Kildare Hill property from the Bank of New Zealand in 1906, recommenced mining and completed the formation of what became known as the Blue Lake.
In spite of such misfortunes, Ewing moved to Dunedin in 1907 to pursue what he described as 'the hydraulic mining enterprise of my dreams': the mining of the supposedly richly auriferous ancient beds of the Clutha River on Andersons Flat below Roxburgh. Despite lack of capital, investor scepticism, entrenched opposition from within the Mines Department, and attacks on his water rights, in 1909 Ewing finally succeeded in registering the Teviot–Molyneux Gold-Mining Company. His enduring optimism, tireless labour and huge investment notwithstanding, this venture failed. In 1912 he aroused the bitter opposition of the St Bathans miners when he attempted to use his prior water rights out of Dunstan Creek to establish an irrigation scheme for the Manuherikia Valley. His health began to fail and by June 1922 he lay seriously ill in Dunedin's Chalet Hospital, where he died on 30 August. Mary Frances Ewing died in 1930 and both are buried in Dunedin's Andersons Bay cemetery.
John Ewing, variously known as 'Big John Ewing', the 'Gold Baron' or the 'Mining Monarch', was a pioneer and progressive leader of the alluvial gold-mining industry, pursuing his occupation with great skill, foresight, tenacity, industry and determination. He had unbounded faith in the industry, possessed a wide practical knowledge of mining geology and engineering, a detailed knowledge of mining law, and an intimate understanding of miners' needs and aspirations. A great reader and raconteur, he was especially fond of Keats, Shelley and Tennyson. Ewing was also capable of both bigotry and great anger and was often harshly critical of those who, in his view, lacked imagination, foresight and understanding. But that he 'loved his calling as a miner', as he himself observed, there can be no doubt.