Jack collaborated with Robert Etheridge, Junior, to produce two classics of Australian geological literature: Catalogue of Works, Papers, Reports and Maps on the Geology, Palaeontology etc. of the Australian continent and Tasmania (1881) and The Geology and Palaeontology of Queensland and New Guinea (1892), and also published several editions of a Geological Map of Queensland.
Jack resigned to work for an English mining company in China, but the onset of the boxer rebellion there caused him with his son, R. Lockhart, to make their way to Burma through some very rough country. Jack worked as a consultant from London between 1901-4, before returning to Australia, where he spent five years in Perth as a consultant, mainly in mining matters (Collie coalfield, mine ventilation and sanitation and lung disease) before moving to Sydney, where he completed his last major work (on exploration), Northmost Australia, published the year of his death.
Jack was recognised by his colleagues by election as first president of the geological section of AAAS (later ANZAAS) in 1888, and he contributed at this time in the important matter of ensuring the regular meeting of geologists from the various colonies to exchange ideas and to co-operate across colonial boundaries. These were important steps in building up a coherent knowledge of the geology of the continent. He was very correct in dress, and generally not assertive, but he was a persistent and active geologist, with a generally democratic outlook that was appreciated by his colleagues.