Rosickyite (monoclinic gamma-sulphur) from La Presta Asphalt Mine, Neuchatel, Switzerland: new X-ray powder diffraction data

Rosickyite, the natural monoclinic gamma -form of sulphur, exists in only a few localities around the globe. In the old asphalt mine at La Presta, Neu chatel. Switzerland, rosickyite occurs locally as small, but very well form ed crystals suitable for crystallographic studies. It grows as an alteratio n product of pyrite-rich asphalt. Rosickyite from La Presta mine is pure mo lecular sulphur, as revealed by gas chromatography-mass spectrometry. The X -ray powder diffraction data of La Presta rosickyite does not match the one previously published for this species. Therefore, a single crystal study w as undertaken and a new indexed X-ray powder diffraction diagram for natura l rosickyite is proposed.