In quartz-seheelite veins traversing rocks from the metamorphic complex in the Central Rhodopian mountains, a mineral was found closely resembling bismuthinite. Its composition is Bi 66·62 %, Pb15·50 %, Cu 0·85 %, and S 16·71 %, corresponding to the formula PbBi₄S₇. It is orthorhombic, long prismatic to acicular with an axial ratio a:b:_c = 0·9004:1:0·3249. Observed forms: {110}, {100}, {010}, and {011}. Sp. gr. 6·92. Hardness about 212 Displays a perfect cleavage along {100}. It is distinctly anisotropic. Strongest X-ray intensities: 3·50 Å. (10), 3·08 (8), 1·939 (8), 2·78 (6), 1·733 (6), 2·50 (5). The name is after the eminent Bulgarian mineralogist and petrographer G. Bonchev.