ard" or "half-metal"; Georgius Agricola used
the form "wissmuth," latinized to "bisemutum," and also the term
"plumbum cineareum." Its elementary nature was imperfectly understood;
and the impure specimens obtained by the early chemists explain, in some
measure, its confusion with tin, lead, antimony, zinc and other metals;
in 1595 Andreas Libavius confused it with antimony, and in 1675 Nicolas
Lemery with zinc. These obscurities began to be finally cleared up with
the researches of Johann Heinrich Pott (1692-1777), a pupil of Stahl,
published in his _Exercitationes chemicae de Wismutho_ (1769), and of N.
Geoffroy, son of Claude Joseph Geoffroy, whose contribution to our
knowledge of this metal appeared in the _Memoires de l'academie
francaise_ for 1753. Torbern Olof Bergman reinvestigated its properties
and determined its reactions; his account, which was published in his
_Opuscula_, contains the first fairly accurate description of the metal.

_Ores and Minerals._--The principal source of bismuth is the native
metal, which is occasionally met with as a mineral, usually in
reticulated and arborescent shapes or as foliated and granular masses
with a crystalline fracture. Although bismuth is readily obtained in
fine crystals by artificial means, yet natural crystals are rare and
usually indistinct; they belong to the rhombohedral system and a
cube-like rhombohedron with interfacial angles of 92 deg. 20' is the
predominating form. There is a perfect cleavage perpendicular to the
trigonal axis of the crystals; the fact that only two (opposite) corners
of the cube-like crystals can be truncated by cleavage at once
distinguishes them from true cubes. When not tarnished, the mineral has
a silver-white colour with a tinge of red, and the lustre is metallic.
Hardness 2-2-1/2; specific gravity 9.70-9.83. The slight variations in
specific gravity are due to the presence of small amounts of arsenic,
sulphur or tellurium, or to enclosed impurities.

Bismuth occurs in metalliferous veins traversing gneiss or clay-slate,
and is usually associated with ores of silver and cobalt. Well-known
localities are Schneeberg in Saxony and Joachimsthal in Bohemia; at the
former it has been found as arborescent groups penetrating brown jasper,
which material has occasionally been cut and polished for small
ornaments. The mineral has been found in some Cornish mines and is
fairly abundant in Bolivia (near Sorata, and at Tasna in Potosi). It is
th