Berryite at Ivigtut, Greenland occurs with other ore minerals and a number of gangue minerals in small massive lumps in the lower part of the siderite-rich cryolite. The structural cell is monoclinic, but the lattice is geometrically orthorhombic, a=12.707, b=4.021, c=28.92A, beta =102 degrees 36'. X-ray powder data are given. Electron microprobe analysis of three mineral grains agree best with the composition: Pb 3 Bi 7 (Ag (sub 1.5) Cu (sub 3.5) )S 16 . This formula has a calculated density of 6.87 for a Z value of 2.

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