Percy A. Wagner, geologist, was the son of John M. Wagner and his wife Bertha Hoffa, both of German origin. He matriculated through the University of the Cape of Good Hope in 1902. During the next two years he studied at the South African School of Mines, then part of the South African College in Cape Town, passing the first mining examination of the University of the Cape of Good Hope in 1904. That year training in mining was transferred to the Transvaal Technical Institute in Johannesburg. Continuing his studies there he passed the university's second mining examination in 1905 and in 1906 was awarded both the Diploma in Mining Engineering and the degree Bachelor of Science (BSc) in Mining Engineering. His first publication, "Petrographical notes on rocks in the vicinity of Craighall [Johannesburg]", appeared in the Transactions of the Geological Society of South Africa in 1907.
Proceeding to Germany Wagner continued his studies at the Sachsische Technische Hochschule, Dresden, in association with the Konichliche Sachsische Bergakademie (Royal Mining Academy of Saxony) in Freiberg, which awarded him the degree Doctor of Engineering (D.Ing) in 1909. His doctoral thesis, Studien an dem diamandf?hrenden Gesteinen s?dafrikas (Studies of the diamond-bearing rocks of South Africa) was published that same year as a book (Berlin, 1909, 207p). He also studied at the Rosenbusch Institute for Petrology at the University of Heidelberg. Upon his return to South Africa he taught geology at the Transvaal University College in Pretoria for some time and for a few months joined the Geological Survey of the Transvaal. He then became a consulting geologist and mining engineer. Among others he carried out geological investigations at Kimberley for De Beers Consolidated Diamond Mines and published a comprehensive overview, The diamond fields of southern Africa (Johannesburg, 1914, 347p; facsimile reprint 1971), which was for many years the most thorough and comprehensive study of the geology of the country's diamond mines. When South Africa took over the administration of German South West Africa (now Namibia) in 1915 the government commissioned him to report on the mineral resources of the territory. His report, The geology and mineral industry of South West Africa (Geological Survey, Memoir No. 7, 1916) described the country's stratigraphy and mineral deposits in some detail. From 1919 he was a full-time geologist in the Geological Survey of South Africa, concentrating on economic geology. In 1927 he left the Geological Survey to become consultant to the Union Minerals Exploration Syndicate in Johannesburg. He died two years later, at the age of only 44, of enteric fever followed by pleurisy and pneumonia.
During his relatively short career Wagner produced three books, seven Geological Survey memoirs, and over 100 papers. He was an extremely hard worker who maintained the highest professional standards. Many of his memoirs and papers were reports on the numerous economic mineral deposits that he investigated: Tin near Cape Town (1909), graphite-coated diamonds from Premier Mine (1914), graphite-bearing Xenoliths from the Jagersfontein Diamond Mine (1916), asbestos, graphite, magnesite, mica, corundum, talc, fluorspar and barytes used in the arts and industries (1917-1919, a series commissioned by the government's Scientific and Technical Committee), corundum of the Zoutpansberg (1918), kimberlite from the Belgian Congo (1921), lead and vanadium in the Transvaal (with M. Fergusson, 1920), mineral occurrences in the Namib Desert (1921), iron ore deposits near Walfish Bay (1921), the Mutue-Fides Stavoren tinfields (1921), the Crocodile River iron deposits (1921), descloizite from South West Africa (1922), chromite of the Bushveld Complex (1923), a Transvaal silver lead deposit (1924), ornamental building stones of the Transvaal (1924), gold near Rustenburg (1927), the Potgietersrus cassiterite pipes (1926), chrome in Zimbabwe and the Transvaal (1930), and many more. With Hans Merensky* as co-author he wrote "The diamond deposits on the coast of Little Namaqualand" (Transactions of the Geological Society of South Africa, 1928). Another major publication was The iron deposits of the Union of South Africa, published as Geological Survey, Memoir No. 26 (1928). He made particularly important contributions to the study of the tin, nickel and platinum deposits of the Bushveld Complex. This work culminated in the publication of his monumental work, The platinum deposits and mines of South Africa (Edinburgh, 1929).
Not all Wagner's work was in economic geology however. He provided a comprehensive description of The Pretoria salt pan, a soda caldera (Geological Survey, Memoir No. 20, 1923), for which the University of Cape Town awarded him the degree Doctor of Science (DSc) in 1922. It included a detailed account of the various saline deposits on the crater floor. He concluded that the crater was the result of volcanic action, but this theory was later rejected in favour of a meteorite impact. General geological papers by him included "The geology of a portion of the Grootfontein District of German South West Africa" (1910), "On an interesting dyke intrusion in the upper Waterberg System" (1912), "The geology of a portion of the Belingwe District, Southern Rhodesia" (1914), "The Dwyka Series in South West Africa" (1915), and "The geology of the neighbourhood of Kanye in Bechuanaland" (1930). In 1929 he participated actively in the meeting of the International Geological Congress in Pretoria, preparing guides to excursions to the Premier Mine, the Pretoria iron deposits, and the Pretoria Salt Pan, and leading these excursions with energy and enthusiasm. At the time of his death he was working on The mineral deposits of the Union of South Africa (Johannesburg, 1930), a handbook that was completed by Leopold Reinecke.
Wagner's interests included the plants associated with different geological formations, prehistoric stone artefacts, and prehistoric smelting operations. He published a paper on "Bronze from an ancient smelter in the Waterberg district, Transvaal" (South African Journal of Science, 1926), followed three years later by "Further notes..." on the same topic, in collaboration with H.S. Gordon (Ibid, 1929). His other extensive archaeological notes had not been published at the time of his death, but he presented the University of the Witwatersrand with a valuable collection of prehistoric mining implements, smelter appliances and metal work. His interests extended also to the living human populations of the regions he visited, particularly their games and pastimes. For example, he published "A contribution to our knowledge of the national game of Africa" in the Transactions of the Royal Society of South Africa (1917) and a "Note on a relic of the phallus cult among the M'Kahtla" in the Annals of the Transvaal Museum (1921).
Wagner became a member of the Geological Society of South Africa in 1905, served on its council from 1910 to 1929, and as president in 1916. That same year he was elected a Fellow of the Royal Society of South Africa. By 1906 he was a member of the South African Association for the Advancement of Science, serving as president of Section B in 1918. Around 1927 he was elected a Fellow of the Geological Society of London. For some time before his death he was associate editor of the Journal of Economic Geology. In his obituary in the Geological Magazine A.L. du Toit* described him as South Africa's "most brilliant geologist" and as "unselfish in character, charming in manner, enthusiastic in discussion, and friendly in debate". In 1922 he married Ida van den Berg, with whom he had a son and a daughter.