ALLEGHANYITE FROM BORODULINSKOYE DEPOSIT OF COMMERCIAL RHODONITE (THE MIDDLE URALS)

摘要

There is the first mineralogical description of alleghanyite from the rhodonite-bearing rocks of the Borodulinskoye deposit of gem rhodonite (the Middle Urals). This mineral takes part in association with rhodochrosite, sonolite, tephroite and galaxite. It is presented by small grains (about 0.5 mm) of braun colour. Optical propeties are n_p = 1.752, n_m= 1 770, n_g = 1.795, -2V= 68-72 deg, aN_p = 26-30 deg. Elementary cell parameter are a =10.760, b =7.910, c=8.270, #beta#=108.45. The chemical composition (SiO_2 24.12, FeO 0.44, MnO 71.31, MgO 0.15, CaO 0.04) corresponds to crystallo-chemical formula (Mn_(4.98Fe_(0.03) Mg_(0.02)_(5.02))(Si_(1.99)O_8) (OH)_2. Specimens with studied alleghanyite have been relayed to mineralogical museum of Mineralogical department of St. Petersburg State University.