480 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
The character of the contact between the granite and breccia, when examined in 
detail, is found to be similar to that described in the Portland. The breccia, contain¬ 
ing abundant fine granitic detritus, fits snugly against a wall of granite, which is far 
too irregular to afford any ground for considering it a fault plane. As in the Port¬ 
land, blocks of granite from 2 to 3 feet in diameter are sometimes found in the breccia 
at a distance of 100 feet or more from the granite in place. The contact is usually 
sharp and definite, though, on account of the granite fragments in the breccia, it is 
not always conspicuous. The granite close to the breccia is seldom breceiated, 
though sometimes considerably jointed and occasionally shattered. 
A basaltic dike, usually from 2 to 4 feet wide, with steep westerly dip, runs 
nearly north and south through the Ajax workings, and is conspicuous on all the 
levels. Above level 3 this dike is practically at the shaft, while on level 10 it passes 
about 100 feet west. It has undergone the usual decomposition and exhibits the 
platy parting parallel to the walls that characterizes the basaltic dikes of the district. 
It cuts squarely across the contact between the granite and the breccia without being 
deflected from its course. While it may practically be considered a single dike, like 
others of its type in the district, it sometimes pinches and is succeeded by a second 
dike lying a few feet to one side or the other of the first, and increasing in width as 
the latter decreases. No ore occurs in the Ajax basaltic dike. 
Many phonolite dikes are encountered in the Ajax, cutting both the granite and 
the breccia. In petrographical character, alteration, and structure they are in every 
way similar to the phonolite dikes of the Portland and other mines in the vicinity. 
They are often exceedingly variable in form, now narrowing or pinching out entirely 
and now branching, widening into irregular masses, or connecting with nearly 
horizontal sheets or sills. Such phonolite dikes as cross the granite-breccia contact 
frequently send off irregular apophyses or branches between the granite and the 
breccia. Most of the dikes, like the lodes, have general northwesterly strikes, but 
some with northeasterly strikes occur in the granite. A few only of the phonolite 
dikes require special mention on account of their relation to the ore bodies. One of 
these is the Apex dike, which accompanies the Apex lode and continues in a south¬ 
easterly direction into the Dead Pine mine, where it is known as the Montana dike. 
This dike, as seen in the Ajax, usually varies in width from 4 to 15 feet, and like 
others of its class is branching and irregular. It forms the hanging wall of the pro¬ 
ductive part of the Apex lode, but in the Ajax mine is not accompanied by any 
important ore bodies along that part of its course which lies in the granite. In the 
Dead Pine and Gold Coin mines, however, it becomes economically important. 
In the granite southwest of the main shaft are some phonolite dikes of general 
northeasterly trend which are related to the large ore bodies of this part of the mine. 
One of these, running almost due southwest from the shaft and dipping about 60° 
NW., is well exposed on level 7, where it is in part mineralized and has been stoped in 
places to a width of 6 or 7 feet. Another smaller dike lying northwest of the last and 
nearly parallel in strike, but with steeper dip, is shown on level 6 passing longitudi¬ 
nally through the great southwest stope in the granite. Possibly there are still 
other dikes comprised in this northeast-southwest zone, but the irregularity of the 
phonolite intrusions and the height of the untimbered stopes preclude the detailed 
tracing out of every dike that may be present. 
