1911 Encyclopædia Britannica/Stibnite

by Leonard James Spencer

STIBNITE, a mineral consisting of antimony sulphide, Sb₂S₃, occurring as bladed or acicuclar orthorhombic crystals; an important ore of antimony. It was mentioned by Dioscorides and Pliny under the names stimmi, stibi and platyophthalmon (πλατυόφθαλμον); the last name refers to the use which the ancients made of the powdered mineral for darkening the eyebrows to increase the apparent size of the eyes. Antimonite is a name in common use for this species. The crystals are prismatic in habit, deeply furrowed longitudinally, and usually terminated by acute pyramidal planes. There is a perfect cleavage (010) parallel to the length of the crystals, and the basal plane (001) is a plane of gliding; the latter gives rise to very characteristic transverse striations or nicks on the cleavage surfaces of crystals which have been bent. The colour is lead-grey, and the lustre metallic and brilliant: crystals become dull on prolonged exposure to light. Cleavage flakes of extreme thinness transmit a small amount of red light, but are more transparent for heat rays. The mineral is quite soft (H.=2), and has a specific gravity of 4·6. Stibnite occurs with quartz in beds and veins in gneisses and schists, or with blende, galena, &c., in metalliferous veins. Magnificent groups of brilliant crystals, up to 20 in. in length, are abundant in the extensive antimony mine of Ichinokawa, province of Iyo, Japan. Large, but dull, crystals have also been found at Lubilhac in Haute-Loire, France. Prismatic and acicular crystals often penetrating tabular crystals of barytes, are common at Felsöbánya near Magy-Bánya and Kremnitz in Hungary.  (L. J. S.)