Rodolicoite e grattarolaite, two new phosphate minerals from Santa Barbara Mine, Italy

Grattarolaite and rodolicoite, two new anhydrous iron phosphates, were found at Santa Barbara lignite mine as reddish-brown nodules. They occur as small crystallites (< 1000 Angstrom), associated in fine-scale intergrowth that prevent the measurement of physical properties. Grattarolaite is trigonal, with space group R3m; rodolicoite is also trigonal, but with space group P3(1)21. Cell dimensions, calculated from X-ray powder patterns, are: grattarolaite a = 7.994(4), c = 6.855(4) Angstrom, V = 379.4 Angstrom(3), Z = 3; rodolicoite a = 5.048(3), c = 11.215(8) Angstrom, V = 247.5 Angstrom(3), Z = 3. The chemical data, obtained by transmission electron microscope microanalysis, give the composition Fe2.99P1.01O7.00 for grattarolaite and Fe1.04P0.96O4.00 for rodolicoite. Infrared spectroscopy and thermal analysis confirm the anhydrous nature of both minerals.