GEOLOGICAL DISTRIBUTION
The geological distribution of commercial antimony depends, with a few exceptions, upon the distribution of the principal ore mineral, stibnite (antimony sulphide). Cervantite, sernarmontite and valentinite are antimony oxides resulting directly from the decomposition of stibnite near the surface, and with other oxidized products form the chief ores of certain districts. Metallic antimony, also a result of oxidation of the sulphides, is rarely found, and still more rarely is it an ore mineral. Jamesonite, the sulphide of antimony and lead, is of frequent occurrence and is the principal ore of one important deposit in Mexico. Antimony is also recovered from the refining of antimonial lead.
Stibnite occurs in quartz veins and related deposits. Many of the important antimony deposits of the world occur in more or less close genetic relationship with eruptives of Tertiary age. The ore often gives way to pyrite with depth. A few important deposits occur in connection with intrusive rocks formed at considerable depth and are probably of contact metamorphic origin.
Although there is a wide diversity in the forms of the deposits and the nature of enclosing rocks, stibnite shows a distinct tendency to form replacements in limestone. The chief gangue minerals are quartz and calcite. Of other sulphides pyrite is the commonest, but cinnabar, realgar, chalcopyrite, galena, and sphalerite are often present as accessories. A characteristic feature of stibnite deposits is the relative scarcity of other sulphides; and it is equally true that important sulphide deposits of other metals rarely contain stibnite. An exception to the general rule is cinnabar, the sulphide of mercury, which is a characteristic mineral of certain stibnite veins. Likewise stibnite is one of the minerals most frequently associated with cinnabar deposits.
Several of the most important antimony districts owe their production of that metal to the presence of recoverable amounts of gold. This is true of certain French, Hungarian, Australian, and South African deposits.