Bismuthinite is a scarce bismuth sulfide mineral (Bi2S3). It's similar to stibnite in its physical properties, and fine-grained specimens are difficult to distinguish visually. Bismuthinite has a metallic luster, silver color, gray streak, one perfect cleavage, is fairly soft (H = 2 to 2.5), and has a high specific gravity (it's heavy for its size). Nicely crystalline specimens often display radiating masses of long, needle-shaped crystals. Finer-grained and massive bismuthinite also occur. Crystals of bismuthinite are known to be slightly flexible, and the crystal faces typically have fine striations.
Bismuthinite is a key ore mineral for the element bismuth (Bi). It principally occurs in hydrothermal vein deposits, some pegmatites, and some volcanic exhalation deposits.
Bismuthinite (silver-colored areas) in pegmatitic granite with quartz (glassy gray material in lower part) & K-feldspar (cream/buff-colored material at upper left) (3.4 cm across at its widest).
Geology: pegmatite body in the Preissac-Lacorne Batholith (Abitibi Greenstone Belt, late Neoarchean, 2.630-2.675 billion years).
Locality: Moly Hill, Quebec, Canada.