Russell Hallack, businessman and naturalist, came to South Africa in 1843 at the age of 19. He settled in Port Elizabeth and remained there for the rest of his life. In April 1849 he maried Sarah Geard. Their youngest daughter, Florence, (later Mrs F.M. Paterson*) became a plant collector. Hallack's participation in public life included serving as a member of the management committee of the Port Elizabeth Athenaeum during the late 1850s, his affiliation at that time being given as "Depository of Bible and Trust Society" (Cape Almanac, 1959, p. 243). In 1862 he served also on the management committee of the Port Elizabeth Public Library. Many years later he reported his measurements of rainfall during 1893 to the Cape of Good Hope Meteorological Commission. In the General directory of South Africa R. Hallack was listed as a grocer (1890/1) and as grocer and coffee merchant (1903) in Port Elizabeth.
In 1866 the Port Elizabeth Natural History Society was founded. Though it survived only about a year, it was a pioneering effort and as far as is known the first of its kind in southern Africa. Hallack participated in its activities and members regarded him as a knowledgeable naturalist. For example, at a meeting on 31 January 1867 some bird skins received from Colesberg and a small snake were referred to him for identification. Fifteen years later he chaired the foundation meeting of the Port Elizabeth Naturalists' Society (1882-1884), which after two years changed its name to the Eastern Province Naturalists' Society (1884-1923). He was its leading member for many years, serving as its first president from 1882 to 1885, and again during 1888-1889, and as vice-president in 1891. In 1888 he was furthermore elected as one of the three trustees of the society. He addressed its members on several occassions, for example on the various orders of plants (26 January 1882), the flora of South Africa (9 February 1882), the birds of South Africa (1882), the timber trees of the southern hemisphere (24 April 1885), and the distribution of the South African flora (1887). In 1890 he guided the curator of the society's herbarium in the mounting of specimens.
Hallack's collecting activities appear to have been confined to plants. He collected in the vicinity of Port Elizabeth and during a journey to Natal in 1854, sending specimens to W.H. Harvey* and later to P. MacOwan*. Harvey thanked him in the preface to Volume 1 of the Flora Capensis (1860) "for interesting information on plants of the Natal Colony, accompanied by specimens obtained on hasty journeys". Many of these specimens represented new species. In 1873 he visited Leopold R. Baur* at his mission station at Baziya in the Transkei and motivated him to resume plant collecting. In 1882 Miss Marrianne North* collected with him during her visit to the town, and described him as a most enthusiastic plant hunter. Four years later E.E. Galpin* also collected with him during a visit to Port Elizabeth.
The plant genus Hallackia (later included in Huttonaea) was named after him by Harvey, and the orchids Satyrium hallackii and Disa hallackii by H. Bolus* and R.A. Rolfe respectively. Some of his specimens are in the Compton Herbarium of the National Botanical Institute in Cape Town.