CHAPTER X.-THE ORE SHOOTS. 
It is well known that the payable ores in auriferous lodes are rarely equally 
distributed in the lode, but form tabular bodies of more or less regular outline. 
The projections of these ore bodies on the plane of the lode often appear as elongated 
areas with greater vertical than horizontal extent. The ore bodies or shoots of 
Cripple Creek show great similarity to those of other gold-bearing veins; their 
limit in depth is usually as well defined as their extent in a horizontal direction. 
The opportunities for the study of ore shoots have been exceptionally good in 
this district, as will be seen from a perusal of the detailed descriptions. If with all 
these observations there remain many doubtful and unexplaihed points in their 
occurrence, this must be laid to the great inherent difficulty of the subject. The 
deposition of ores depends not only on structural features, but also on imperfectly 
known laws of precipitation from complex solutions at high temperatures and 
pressures. 
DIMENSIONS AND PITCH OF THE SHOOTS. 
The general statement that the ore shoots are tabular bodies is based on the 
fact that the ore follows vein fissures and sheeted zones, and that consequently the 
thickness may be considered constant. In reality the thickness varies considerably. 
In some veins almost the whole value is concentrated in a central seam, although 
a width of 3 feet must be extracted on account of mining requirements. The most 
common case is that while the greater values are in one or two central seams a num¬ 
ber of others also contain friable ore, which is extracted by screening the whole 
thickness taken out, say 4 feet. Frequently, however, the width containing valuable 
seams increases to 10 or even 20 feet, while in exceptional cases of many coalescing 
sheeted zones the stopes may attain a width of 50 feet, as in the Captain veins of 
the Portland mine. In gold-bearing veins consisting of thick quartz filling it is not 
uncommon for a certain width of this vein to contain the valuable ore, while the 
remainder may be of very low grade. * Such a condition, which is apt to be caused 
by a reopening of the vein fissure and attendant enrichment, does not often occur 
in this district. A somewhat similar state of affairs has been observed in the Blue 
Bird mine, where the ore in places follows spar veinlets which are later than the 
main filling of “purple quartz.” 
If we assume that the shoot has an elongated, narrow shape, as usually is the 
case when projected on the plane of the vein, its geometrical relations may be des¬ 
ignated as follows; Width or thickness, breadth, stope length, pitch length, and 
pitch. The thickness or width has already been discussed; the stope length is the 
distance along the drifts over which payable ore extends; the pitch length, or 
axial length, as it might also be termed, is the distance between the two extreme 
ends of the shoot; the pitch is the angle which the pitch length makes with the 
horizontal; the breadth is the horizontal width multiplied by the sine of the pitch. 
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