Charles ("Charley") Sirr Orpen, amateur geologist and genealogical researcher, was one of the nine children of Reverend Dr Charles Edward Herbert Orpen (MD), member of a family of Irish landed gentry, and his wife Alicia Francis Coane (born Sirr). Two of his brothers were Francis H.S. Orpen* and Joseph M. Orpen*. Charles junior emigrated to South Africa in 1844 with his brother Francis. During the next few years the rest of the family followed them to South Africa, where Charles senior financed his sons' farming venture on the farm Taai Bosch Fontein near De Aar. Charles junior later became a law agent at Smithfield in the Free State. On 17 March 1854 he married Rosetta Lucas (1832-1873) with whom he had eight children. That year he was charged with the murder of a Bushman, named Klaas, near Jackals Water [not identified] in the Beaufort West district, but it is not clear whether he was found guilty. As church warden of the Church of England at Smithfield he was responsible for the publication of the correspondence of the church committee with the newly appointed Bishop of the Orange Free State, Edward Twells, with whom the committee had some disagreements. The publication was entitled State of the Church of England mission to the Orange Free State (Grahamstown, 1865). Later he compiled A comprehensive abstract of the marriage laws of the countries comprised in the Diocese of Bloemfontein..., a pamphlet published in Bloemfontein in 1887.
In 1848 Charles accompanied the hunter-explorer R.G. Gordon Cumming* on a journey to the Limpopo Valley. Subsequently he devoted his spare time to geology, fossil collection, and archaeology. In August 1855 he wrote a paper on "Gold in greenstone" which does not appear to have been published, but was included in the T.R. Jones* collection of papers and manuscripts relating to the geology of South Africa. That same year he wrote a paper on the white sands of the Kalahari, which was read before the Grahamstown Medico-Chirurgical Society in December by Dr W.G. Atherstone*.
Some time before 1880 Charles showed George W. Stow* a small cave near Smithfield, which they excavated together. The deposit contained bone fragments, pieces of ostrich eggshell, freshwater shells, numerous stone artefacts, pieces of pottery, a bone arrow shaft, and a fragment of a clay pipe stem. This excavation appears to have been the first reported archaeological excavation of a shelter in the interior of South Africa. Stow described the work years later in his book The native races of South Africa (1905) and concluded that shelter excavations can yield useful archaeological information.
By 1877 Charles had accumulated an extensive collection of particularly geological specimens, fossils, and archaeological and ethnological artefacts. In July that year he enthusiastically supported a movement to found the National Museum of the Orange Free State in Bloemfontein, promising to donate his collection to form the nucleus of the new museum. He was elected a corresponding member of the museum committee and assisted in the committee's efforts to obtain suitable museum material from the public. His own donations included archaeological artefacts in August 1877 and fossils and geological specimens early in 1878. However, his main collection was not received, as it had been made over to the Scottish Masonic Lodge in Smithfield. The museum committee opened negotiations with the masters of the lodge, with the result that the collection was received around the middle of 1879. Charles's genealogical tables of Sotho and Tswana clans are in the National Library, Cape Town.