RELATION OF ORE SHOOTS TO SURFACE-. 
207 
begin distinctly below the surface the elongated form is more strongly accentuated, 
the ratio between pitch length and breadth varying from 1^:1 to 5:1. 
A few of the large ore shoots are practically equidimensional. This is more 
generall} 7- the case with the small shoots and here the horizontal extent is in a few 
instances greater than the vertical. 
Sometimes the outlines are wholly irregular, and as the exact limit between 
what are considered the payable and barren portions of the vein is an arbitrary 
one, depending on local facilities and price of production, areas are often left 
unstoped in the middle of a shoot which properly belong to it. The Gold Coin 
mine, for example, has stoped squarely up to the line separating this mine from the 
Dead Pine mine. The smaller Dead Pine mine, however, can not work this ore, 
which here happens to to be low grade, so that stope maps give the false impression 
that the Gold Coin ore body ends at the Dead Pine line. Where the shoot has its 
normal elongated form it is very common to find little pockets or irregular masses 
of ore just above and below the points where it begins or ends. Thus, in the Isabella 
mine, small masses of ore were frequently found in the lower levels underneath the 
places where the ore shoot is developed in force above. The same is observed at 
many other mines and may in fact be considered as a general rule. 
The outlines of the shoots are not usually limited by fissures or seams. Pen¬ 
rose describes such a case from the C. O. D. mine, and similar cases may be noted 
here and there. In the Gold Coin mine, for instance, the Cashen fault is the dividing 
line between the barren and the productive zone. Ordinarily, however, there are 
no such limiting seams. On the contrary, the ore gradually grows thinner and 
poorer toward the outside, begins to get bunchy, and finally ceases altogether, 
while the vein may continue as before in its general character, except that the 
calaverite is absent. Frequently, however, the limit of the ore shoot is attended 
with diminution in the width and strength of the sheeted zone. 
When one ore shoot ceases in depth it is often observed that another one, 
somewhat overlapping, is apt to come in on an adjoining fissure. In some lodes 
the ore shoot as a whole is really a succession of imbricated bodies on adjoining 
planes. 
Thorough exploration of the surroundings of a prominent ore shoot will prob¬ 
ably be rewarded by the discovery of smaller bodies underneath, in the main 
direction of pitch. 
RELATION TO SURFACE. 
Of 60 pay shoots of Cripple Creek mines plotted together for purposes of com¬ 
parison, 30 extend from the surface to a depth of less than 500 feet. The maximum 
individual production of these is less than $1,000,000. 
Near 6 of these ore bodies further exploration developed new shoots below 
the old ones, but usually of smaller extent. In practically all 30 cases the devel¬ 
opment work had been carried down a few hundred feet below the last ore of the 
surface shoot. The form of these smaller shoots is often equidimensional; in a few 
cases the horizontal extent is greater than the vertical, or the shoot is wholly 
irregular; in many cases the shoot pitches steeply northward on the plane of the 
vein and the ratio of vertical to horizontal extent is 2:1 or 3:1. 
