BIS3 UTH, a metal that was unknown to the ancients. It was referred to by Agricola in his work on mining in 1529, and was subse quently described by Stahl and Dufay.
The minerals in which this metal constitutes the principal ingredient are comparatively few in number ; and of these only two species are of any importance in a commercial point of view, namely, the native bismuth, and its sulphurets. The general characters of these minerals are the following. Before the blow-pipe they are readily fused and reduced to a metallic state, the regulus itself gradually subliming if the flame be continued, leaving on the charcoal an orange-yellow areola, which however may readily be made to disappear in the deoxidising flame. When the metallic regulus is fused in an open glass tube, a yellowish-white sublimate is obtained, and the regulus itself becomes covered by the fused oxide, which while hot is of a dark brown colour but assumes a yellow tint on cooling. These minerals are all of them soluble in strong nitric acid, the solution yielding a white precipitate on being dropped into water. They are known and described by mineralogists under the following names : Native or Octahedral Bismuth, Bismuth-Ochre, Prismatic Bismuth Glance, Needle-Ore or A cicalar Bismuth-Glance, called by Phillips Plumbo-Cuprtferous Sulphuret of Bismuth, Tellurbitanuth, formerly known by the name of Molybdan Silver.
Native or Octahedral Bismuth is sometimes found crystallised : the observed forms are the octahedron, the tetrahedron, and combinations of the latter with the dodecahedron, which produce the shape seen in the accompanying figure.
The faces marked o belong to the tetrahedron and those marked with d to the rhombic dodecahedron. The edge between the faces o is therefore 70° 32', between the faces d 120°, and in the edges of com bination between o and d 144° 44'. These crystals are generally very imperfect, and the faces rough and uneven ; they possess a perfect cleavage parallel to the faces of the octahedron. The hardness varies from 2 to the specific gravity from 9'6 to 9.8. The crystals are opaque, possess the metallic lustre, and the fresh fracture presents a reddish silver white ; but the surface is usually tarnished, owing to partial oxidation, and presents a variegated appearance of gray, red, and blue colours. They may be considered as presenting us with the metal Bismuth in a pure state, the only foreign matter being traces of arsenic. The occurrence of crystals is somewhat rare, this mineral being usually found in feathery and arborescent forms, and also in dentiform concretions in veins, traversing gneiss, mica, and clay-slates, where it is usually accompanied by ores of silver, cobalt, nickel, and iron. It is found at St. Colomb and
Botallack mines in Cornwall, and at Citstle-Carrock in Cumberland, but in much greater abundance in the mines of Saxony and Bohemia, at Johann-Oeorgeustadt, Annaberg, Altenberg, Schneeberg, and at Joachimsthal, from whence the greater portion of the Bismuth of commerce is obtained. It is also found at Beiber in Hainan, at Loling in Carinthia, and in the Sophia mine at Witticheu in Fiirstenberg.
The Bismuth-Ochre is a rare mineral, which occurs massive and disseminated. It is of a straw-yellow, passing sometimes into a light yellowish gray. Its specific gravity is 4'36, and its chemical constitution— Bismuth . - . . . . 89'87 Oxygen . 1013It usually contains small quantities of arsenic and oxide of iron as impurities. Its known localities are St. Agnes, Cornwall ; Schneeberg and Johann-Georgenstadt, in Saxony ; and Joachimsthal, in Bohemia.
Bismutite, a Carbonate of Bismuth, occurs in four sided prisms of unknown dimensions, but it is stated by Phillips to have angles about 91° and 89'. It is further characterised by its metallic lustre, and lead-gray approaching steel-gray colour, and from its possessing a perfect cleavage in the direction of the short diagonal, and one less perfect in the direction of the base. According to Mobs the hardness is between 2 and 2.5, and the specific gravity It also occurs massive of a granular composition, or columnar, the individuals being long and straight, and aggregated in various directions. According to the analysis of H. Rose of a specimen from Reddarhyttan, it is thus composed :— Sulphur . . . 18'49 . . . 18.72 Bismuth . . . . . . . . 80.98Before the blow-pipe sulphur is first driven off, which is followed by a sublimate having the odour of tellurium, and afterwards the characters are the same as those of the other minerals of Bismuth.
Bismuth-Bleiule is a Silicate of Bismuth.
Other minerals in which Bismuth occurs are Needle-Ore and Tellur bismuth. Needle-Ore is also called Acicular Bismuth. It is a sulphuret of bismuth, lead, and copper, containing a trace of gold. It comes from Siberia. Tellurbismuth, or Tetradymite, is composed of tellurium and bismuth. It has a foliated structure, and a pale steel gray colour. It comes from Schemnitz, and also from Brazil.
(Dana, Mineralogy.)