Dr. Roger Stuart Harker was a British mineralogist, geologist, university lecturer, mineral dealer, and co-founder of the Russell Society in 1972 alongside Bob King. The Society emerged from evening classes on mineralogy that Harker and King ran in Leicester.
Harker studied geology at the University of Leicester, completing his undergraduate degree and continuing for postgraduate research. In 1966, after returning to Leicester, he opened his mineral dealership Lythe Minerals, operating from Lythe House in Grassington and later from 2 Wellsic Lane, Rothley, Leicestershire. He married his wife Susan in 1970 and achieved his PhD in geology at Leicester.
As a dealer and collector, Harker built an exceptional collection of British minerals, particularly strong in specimens from Weardale, the Lake District (especially Caldbeck Fells), Derbyshire, Cornwall, and the East Midlands. He maintained extensive field notebooks documenting his collecting trips and site data from 1962 through the mid-1970s. His specimens are instantly recognizable by his distinctive minuscule but highly legible handwriting on labels, which meticulously recorded provenance, collection dates, and locality details.
Harker was deeply embedded in the British mineral-collecting network, acquiring specimens from and collaborating with prominent collectors including Bob King, Ralph A. Sutcliffe, G.J. Lane, R.W. Barstow, and A. Raistrick. He actively participated in specimen exchanges and acquired material from significant older collections, including pieces originally collected by Amos Treloar and Sir Arthur Russell.
