Gustavite with variable Bi/Sb ratio from Kutna Hora deposit, Czech Republic, a new occurrence

Gustavite associated with stibnite and jamesonite was newly found and ident ified from the Starocech (Old Bohemian) Lode, Kutna Hora, Czech Republic. X -ray powder diffraction data and results of electron microprobe analysis ar e presented in the paper. Cell parameters have been calculated. Gustavite h as a monoclinic unit cell with a = 7.064 (1), b = 19.627(4), c = 8.211(2) A ngstrom, beta = 107.20(2)degrees. Two different samples were analysed by th e microprobe analysis. N-chem and L% values have been calculated. The avera ge of six point analyses of gustavite described as crystal in cavity is 4.0 Gus(99.1). The average of 5 point analyses of gustavite described as grain in quartz is (4.00)Gus(100.3). Existence of a fully substituted gustavite f rom Kutna Hora deposit has been confirmed. The gustavite specimens show a s ignificantly variable Bi/Sb ratio within a single grain or crystal with inc reasing substitution of antimony for bismuth from the centre of the crystal s to the rim.