474 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
nests of fluorite and abundant finely disseminated pyrite. The gold, however, is 
apparently limited to the veinlets. 
The microscope shows that the molybdenite occurs as a coating or envelope 
about crystals of pyrite. The principal alteration of the phonolite in the vein 
walls consists in the complete change of the pyroxene or amphibole to aggregates 
of pyrite, apatite, and an obscure yellowish-brown material resembling limonite. 
The feldspathic constituents of the phonolite are partly sericitized. 
FORM AND STRUCTURE OF THE ORE BODIES. 
Nearly all of the ore thus far discovered lies south of the granite-breccia con¬ 
tact. A little ore, it is true, has been stoped from the Bobtail for a distance of 150 
feet southeast of the point where the lode meets the basalt dike, but it was of low 
grade. The lode lying northeast of the Bobtail, on the same level, is a well-defined 
sheeted zone carrying much fluorite and pyrite but no ore. Within the granite 
the ore occurs as lodes along sheeted zones, particularly where these cut or follow 
phonolite dikes and as irregular bunches at the intersections of fissures. 
The principal pay shoot is on the Granite lode. Although not continuously 
stoped, this pay shoot may be considered as extending from a point about 100 feet 
above level 5 down to level 9. Below level 9 the ore apparently left the Granite 
sheeted zone and followed a branch or intersecting lode, with a westerly dip of about 
60°. On level 10 the same lode lies between the Granite and West lodes. Owing 
to its relatively flat westerly dip, it joins the Granite lode between levels 9 and 10. 
The main Granite pay shoot reaches its greatest development between levels 
6 and 7, with a maximum length of about 350 feet. Above level 7 the general 
pitch of the pay shoot is northerly, while below this level it is southerly. Seen in 
longitudinal section the ore body is rudely crescentic in outline, with the horns of 
the crescent turned south. Above level 8 the ore is said to have terminated north¬ 
ward at the granite-breccia contact. 
While the Granite lode is generally a narrow sheeted zone of the usual type, 
at certain points the ore has been stoped to widths of 30 or 40 feet. On level 6 the 
widest ore occurred close to the contact of the granite with the breccia, where some 
additional fissures join the Granite lode from the north-northwest. On level 7 the 
largest body was at the intersection of the Granite and Cross lodes, the ore narrowing 
from a maximum width of 40 feet at the Cross lode to a few inches near the contact. 
In all cases unusual width of ore in the Granite lode is associated with the inter¬ 
section or junction of the main lode with minor fissures. Bodies of good ore fre- 
cpiently occur where the sheeted zone cuts through a mass of phonolite, as on level 9, 
about 400 feet south of the shaft. 
At the time of visit most of the ore was coming from the southern part of 
level 10, where a north-south sheeted zone which may prove to be the continuation 
of either the Granite or the East lode traverses the irregular sill-like offshoot from 
the east-west phonolite dike. This ore is from 8 to 9 feet in width. The lode 
consists of two small, approximately parallel vuggy veinlets of quartz, about 8 feet 
apart. Between these the phonolite is rather irregularly fractured and seamed 
with minute stringers of quartz and fluorite. The value of the ore lies in these 
