Louis de Launay entered the Ecole des Mines (Mining College) at Paris in 1881. He was subsequently appointed as inspector of mines at Moulins (1885) and Dijon (1889), but in the latter year became professor of applied geology at the Ecole des Mines, remaining at the institution until his retirement in 1935. He became a member of the French AcadÃ©mie des Sciences in 1912, and was its president in 1931. Known particularly for his work on the origin of metalliferous deposits, he published several books (in French) on the subject: on the geology, metallurgy and economic role of silver (1896), the mineral wealth of Africa (1903), the formation of metalliferous seams (1905), the ore deposits of Italy (1906), the world's gold (English translation 1908), the geology and mineral resources of Asia (1911), and a three volume Traite de Metallogenie (1913). Other important books by him are a treatise on the geology and chemistry of mineral waters (1899), a dictionary of geology (1901), a book on the geology of France (1921), and another on engineering geology (1922). He also published some papers on historical figures such as AmpÃ¨re and Descartes, and descriptions of his travels.
De Launay also published extensively on the geology of South Africa between 1891 and 1907, mainly on its diamond and gold deposits and mines, and mainly in French. His first three relevant papers dealt with the gold mines of the Transvaal (1891), new gold discoveries in the Cape Colony (1892), and the geological nature of the gold-bearing conglomerates of the Witwatersrand (1892). He visited South Africa at some time before 1896, for in that year he published a practical treatise, Les mines d'or du Transvaal, dealing with various aspects of the Witwatersrand gold mines, as well as those in the Heidelberg and Klerksdorp districts. It contains a chapter on the geology of South Africa, in which the geological structure is simplified by correlating the Table Mountain sandstone with the Witwatersrand beds, and the Witteberg quartzite with that of the Magaliesberg. The Witwatersrand beds are described in some detail, with the discrepancies and mistakes found in most similar accounts at that time. He was convinced that the Karoo strata had formerly covered the whole Witwatersrand region, collected fossil plants from shales of the Beaufort beds south of Johannesburg, and in 1897 published a paper on "The Karroo formation of South Africa" in the London Colliery Guardian. With regard to the conditions under which the Witwatersrand sediments were deposited, his preference was for a marine beach origin, among others because of the vast extent of the formations, the regularity of the beds, and the frequency of shingle-type pebbles. The gold in the conglomerates he thought might have been deposited from solution in the water in which the beds were laid down. In addition to his book he contributed a paper, "Geological description of the gold-mines of the Transvaal (Witwatersrand, Heidelberg, and Klerksdorp districts)" to the Federated Institute of Mining Engineers in London, on 5 June 1896, and had it published in their Transactions. Some years later his "Observations on the Rand conglomerate" appeared in the Engineering and Mining Journal (New York, 1903).
In a second book on South Africa, Les diamants du Cap, a practical and geological treatise on diamond mining published in 1897, De Launay dealt with the history, economics, geology, and working of the diamond fields in the Cape Colony and compared them to diamond fields in Brazil, India, Borneo and Australia. Two of his papers dealing with the diamondiferous rocks of the Cape were published in the Comptes Rendus Hebdomadaires des Seances de l'Academie des Sciences, Paris, in 1895 and 1907.