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November-December 2017

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Who's Who in Mineral Names: Robert Sielecki (b. 1958)

Sieleckiite, Cu3Al4(PO4)2(OH)12·2H2O, is a hydrated copper aluminium phosphate that forms during the oxidation of base-metal sulfide minerals. The type locality is the Mount Oxide copper mine, Gunpowder district, in northern Queensland, Australia, where it occurs, very sparsely, in association with other phosphates including libethenite, turquoise, variscite, minor pseudomalachite, and, rarely, cyanotrichite (a copper aluminium sulfate) on quartzite and shale (Day and Beyer 1996). The mineral is named for its discoverer, Robert “Rob” Sielecki, an Australian geologist and mineral dealer based in Melbourne. Collecting on the dumps at Mount Oxide in the mid-1980s, Sielecki saw a seam of blue material that, when broken, revealed bright blue spherules of a mineral he could not identify but which was later described as sieleckiite (Birch and Pring 1988). Sieleckiite crystallizes in the triclinic system and occurs as sky-blue to royal-blue spheres to 0.5 mm in diameter. These spheres are composed of radial aggregates of fibrous microcrystals, each between 20 and 100 μm long and 1–2 μm wide (Birch and Pring 1988). Sieleckiite remains an extremely rare mineral, although it has subsequently been reported from two other localities: the Girilambone copper mine in New South Wales, Australia (Chapman, Sharpe, and Williams 2005), and Wheal Gorland, Cornwall, in the United Kingdom (Rumsey and Cressey 2010).

Robert Sielecki was born in Melbourne, Australia, on 6 June 1958, the son of Tadeusz (Ted) and Jacoba (Coby) Sielecki. As a five-year-old, he remembers collecting agates and petrified wood with an uncle in New South Wales, and he still owns some of those early agate specimens. His interest in minerals began a little later when, at age thirteen, his parents bought him a Brazilian amethyst cluster for his birthday that absolutely fascinated him and is still in his collection. He enjoyed science at school and started his university studies by reading mathematics and physics before following his passion and switching to geology, which was much more in line with his mineral interest. 


Dr. Malcolm Southwood has collected minerals for more than thirty-five years and is a mineralogist by training. His special interests are the minerals of southern Africa and southwest England.

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