118 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
southwest directions, and that later, following a period of mineral- 
ization and Assuring and faulting in northwest-southeast directions, 
recurrent Assuring and faulting took place on northeast-southwest 
planes. It is in connection with the great limestones which have 
thus suffered intrusion and recurrent Assuring and faulting at several 
periods that the larger bodies of copper ore occur, and in the fissures 
that the smaller but valuable bodies of lead-silver ore formed. 
The copper-sulphide ores occur in the general form of flat, attenu- 
ated lenses, mainly Avithin the great" limestone beds, and lie roughly 
parallel with the stratification. In the vicinity of fissures these bed- 
ded ore bodies thicken into well-marked shoots which, following the 
trends of the fissures, often pitch slightly. When these shoots display 
distinct structure, that of the original stratification is seen to be per- 
fectly preserved. 
The fissure ores carrying lead and silver, with subordinate amounts 
of gold and considerable zinc, differ much from the copper ores in 
the character of their occurrence. They form tabular bodies which 
mayor may not be sharply limited by fissure walls, and extend sev- 
eral hundred foot horizontally and in depth. These lodes occur as a 
series of thin, sinuous, irregular pay streaks, which combined consti- 
tute bodies which are relatively thin when the fissures lie in a quart zite 
or porphyry country, but arc of much greater width where the fissures 
cut calcareous bods. This selective act ion, indicated by bulging or 
increased lateral extent, which is exhibited between calcareous and 
noncalcareous rocks, is manifested in precisely similar manner 
between different bods of the same calcareous mineral. In addition 
to this change in the size of fissure veins, lesser variations occur, 
within lenses lying in a noncalcareous country, which constitute rec- 
ognized shoots. The structure of the fissure ore consists of a rough 
banding of the several constituent minerals which form the vein, in 
roughly systematic arrangement 'from the center of the vein to either 
wall. In brief, there is a rough comb or crustified structure. 
The copper- gold ores inclosed in the porphyry of the Bingham lac- 
colith, however, present an interesting form of occurrence of an 
entirely different character. This ore, which consists of grains of 
cupriferous pyrite and chalcopyrite, is thoroughly disseminated 
throughout the intrusive mass, and seems to increase slightly in value 
in the areas which have suffered the maximum shattering and 
crushing. 
The facts which have been observed with regard to the occurrence 
of the ore deposits of Bingham afford evidence for a very reasonable 
explanation of their formation, and these conclusions lead to several 
suggestions which it is hoped may prove to possess much commercial 
value. As the present abstract does not admit of such theoretical 
discussions, however, they must be deferred until the publication of 
the complete report. 
