Simpson arrived in Western Australia at the height of the 1890s Kalgoorlie gold rush, and his initial work was on the highly metasomatized rocks of the Golden Mile and those throughout the Eastern Goldfields that hosted the chief gold deposits. Probably his best-known scientific contributions were on the niobium, tantalum, uranium and beryllium-bearing minerals from pegmatites in the Pilbara. Finding his work hampered by the lack of accurate methods for the determination of tantalum and niobium, he devised one which for many years was the standard commercial method. He was particularly successful in determining the compositions of complex mineral groups, such as the euxenite-polycrase, rutile-tapiolite, and chloritoid groups. Simpson described four new minerals from Western Australia (that are still valid today), and the mineral simpsonite [Al4(Ta,Nb)3O13(OH,F)], named in his honour, was first described from Tabba Tabba in the Pilbara. Simpson was an authority on clays, rare minerals and meteorites, and was also highly regarded for his research on ceramics.
Some of Simpson’s analytical work on specimens of ‘pilbarite’, mackintoshite and thorogummite from a pegmatite at Wodgina, and fergusonite from a pegmatite at Cooglegong in the Pilbara, was to have an influential legacy on the science of geochronology. In the wake of a visit to Western Australia by Frederick Soddy in 1904, who was a leader in the new field of radioactivity, Simpson had determined the uranium, helium and lead contents of these uranium-rich minerals. Strangely, Simpson failed to calculate the ages of these minerals at the time, but his work was later used by Arthur Holmes to derive a composite age of 1260 Ma for these Pilbara rocks. Holmes included this date in his influential book ‘The Age of the Earth’, published in 1927, in which it was the oldest age recorded. Although this age for the Pilbara minerals later proved to be far too young, Holmes’ book popularised the view that the Precambrian of Western Australia contained the oldest rocks on Earth.
Simpson contributed greatly to the educational, scientific, civic and cultural life of Western Australia. Between 1899 and 1905 he helped to establish the Western Australian School of Mines and joined its advisory board (1902–15). In 1921–26 he was a member of the university senate and from 1927 was government representative on the Western Australian committee of the Council for Scientific and Industrial Research. From September 1935 until his death in 1939, Simpson was a Trustee of the Western Australian Museum and Art Gallery. He was a founder and one-time president of the Natural History and Science Society of Western Australia, and later of the Royal Society of Western Australia which grew out of it. He also served as the president of the Chemical Society of Western Australia and of the State branch of the Australian Chemical Institute. Simpson published over 100 scientific papers and monographs, and received many honours for his work. In 1917 he was elected a Life Fellow of the Chemical Society of London, and in 1926 became a fellow of the Mineralogical Society of America. In 1929 the local Royal Society awarded him its Kelvin gold medal, and the Royal Society of New South Wales followed in 1934 with award of its W.B. Clarke memorial medal.
Simpson’s legacy continues to exert a great influence on mineralogy in Western Australia. It includes his fine work, ‘Minerals of Western Australia’, and his mineral collection, now housed at the Western Australian Museum, that remains a superb reference collection for the minerals of the State.
Peter Downes and Alex Bevan