A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...

54 THE METALLURGY OF ANTIMONY.
The principal antimony veins, in the neighbourhoods of Valongo,
Paredes, and Gondomar, in the district of Oporto, may be roughly
divided into two systems, according to the directions of their strikes.
The one system has a strike, N. 10° to 20° W., coinciding with that of
the country, and hence the deposits may be described as bed-like lodes ;
and the system has a course N. 30° to 60° E. Both of these occur in
Silurian rocks. Near the town of Alcontim, in the district of Faro,
there occur two distinct lodes : one running E.-W. and the other N.W.,
the latter of which has the same strike as the country. These occur
in the slates of the Culm formation. Besides these localities may be
mentioned Braganza.
ALGIERS.
The antimony deposits of Sidi-Bgheis are situated in the southwestern
part of the province of Constantine, and have been mined at
Sempsa and Djebel-Hamimat. They occur in the clays and limestones
of the Lower Neocomian. The ore, according to Coquand, is in part
a compact antimony oxide, and in part a granular crystalline variety
containing senarinontite. At times the oxide deposits may be
superimposed by bundles of stibnite needles. The deposits possess
little gang no and are generally in the form of very irregular masses,
parallel to the plane of stratification. According to Beck, they are
impregnations (C), while de Laxinay classifies them under sedimentary
deposits, and Coqxxand considers them to be contemporaneous with the
enclosing rocks. (E.)
At Djebel-Taia, stibnite is associated with cinnabar.
TURKEY.
At Allchar, in Macedonia, the antimony deposit is found associated
with a great quantity of realgar, together with orpiment. The
sulphur is undoubtedly derived from the decomposition of stibnite,
and is the principal agent in changing many of the oxides intosulphides
; while, together with oxygen, it transforms the neighbouring
chalk into gypsum. This deposit is a good example of paragenesis.
Other antimony ore localities are Adrianopolis, Monastir, Bozdan,
Mytilene, Chios, Aidin, Eudemisch.
SWEDEN.
At Sala, in Westmannland, a small quantity of native antimony
is found associated with the argentiferous lead ore It occurs in the
primitive formations.