Medaite occurs in small brown grains, associated with tiragalloite (M.A. 81-2383), in veinlets cutting braunite and quartz from an abandoned Mn mine at Molinello, near Chiavari, Liguria, Italy. It has the longest sorosilicate ion discovered so far. Medaite is biaxial (+) with alpha 1.77, beta 1.78, gamma 1.80, 2Vgamma 71o (calc.). It is faintly pleochroic (dark to clear orange). The ideal formula is Mn(VSi5O18(OH)); the microprobe formula is also given. D 3.70 g/cm3; Dcalc. 3.750 g/cm3. It is monoclinic P21/n with a 6.712, b 28.948, c 7.578 A, beta 95.4o (M.A. 83M/1199). The strongest XRD lines are 3.259(100), 3.159(83), 3.097(70), 2.613(69), 2.941(68) A.-K.A.R.
|Number of pages||5|
|Publication status||Published - 1982|