NATURAL FERROUS SUBSTITUTED SALEEITE FROM ARCU SU LINNARBU, CAPOTERRA, CAGLIARI, SARDINIA

Ferrous substituted saleeite is a new variety of saleeite from Arcu su Linnarbu, Sardinia. It is tetragonal with a = 6.982(2) c = 19.660(2) Angstrom, Z = 2; the ideal formula is (Mg,Fe2+)(UO2)(2) . 4H(2)O. The strongest lines in the X-ray powder diffraction pattern are: 3.473(100 )(114), 4.95(50)(110), 4.91(40)(004), 4.443(40)(112), 2.200(30)(118), 2.193(30)(303) adn 2.178(30)(009). The mineral is light-yellow in colo ur and is dull fluorescent. The measured density is 3.242 g/cm(3) and Z = 2. There is a prominent (001) clevage. Refractive indices are : al pha = 1.572(2) beta = 1.577(2) gamma = 1.581(2) and 2V = 48 degrees(2) . The pleochroism is very weak and the elongation is positive parallel to Y. The mineral occurs as subparallel crystal aggregates with a qua dratic outline.