468 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
change in the strike of the dike, but a local reversal of dip between levels 3 and 5 
from 40° SW. to about 80° SE. Such irregularity, however, is in full accord with the 
observed behavior of other phonolite dikes in the granite, as may be seen, for 
example, in the Gold Coin mine. 
Below level 5 the cross dike, while retaining its north-northwest strike, resumes 
its southwesterly dip. It is apparently not exposed on levels 6 and 7, but is well 
shown on level 8, 470 feet north of the shaft, and on level 9, 450 feet north of the 
shaft. Its dip in the lower part of the mine thus appears to be about 75° SW. 
In addition to the phonolite dikes there is in the Strong mine a basic dike which 
is important from its relations to the ore bodies. This dike has the same general 
course as the main phonolite dike, lying sometimes on one side and sometimes 
on the other side of the latter. The “basalt” dike cuts the phonolite dike and 
is therefore younger. It is probably not perfectly continuous, but pinches out 
locally to appear again in another parallel fissure a few feet to the east or west. 
The width of the dike varies from a fraction of an inch up to 3 feet. The usual 
width is about 18 inches. The rock is generally rather soft and decomposed, 
exhibiting the fine platy parting and calcitic veining parallel with the walls which 
is characteristic of the basic dikes in this district. The only trace of the dike 
seen on level 1, is a little streak of decomposed “basalt” lying between the ore 
and the main phonolite dike, about 100 feet south of the shaft. On level 3, how¬ 
ever, the “basalt ” dike is well developed, lying from 25 to 40 feet east of the shaft. 
It has been drifted on here for about 200 feet, but is not exposed in the northern 
part of the level. On level 5 the dike lies 40 feet east of the shaft and is here coin¬ 
cident with the Strong lode. The ore leaves the dike, however, about 125 feet 
north of the shaft, the dike lying in the east wall. About 250 feet north of the 
shaft the dike is offset about 15 feet at a cross fissure. While this cross fissure 
may possibly be a fault, of later age than the dike, close examination rather indi¬ 
cates that this offset of the north-south fissure existed before the intrusion of the 
basalt. The general relations of the “ basalt ” dike to the phonolite dikes and to the 
Strong lode on level 5 are shown in PI. Y (p. 26). On level 6 the “basalt ” is first 
seen about 250 feet north of the shaft and is thence followed northward by the 
main drift. About 450 feet north of the shaft the main phonolite dike appears, 
and from here to the north end of the level both dikes run together, the “basalt’ 
cutting across from one side to the other of the phonolite. A similar relation 
between the two dikes exists also on level 7. On level 8 the dike is drifted on 
about 50 feet east of the shaft, and appears again in the northern part of the level, 
where it accompanies the phonolite dike. On level 9 also the basic dike lies 40 
or 50 feet east of the shaft, but about 100 feet north of the shaft it turns nearly 
north-northwest, running about 100 feet southwest of and nearly parallel with 
the phonolite cross dike. This is probably an offshoot from the main dike along 
some branch fissure; in which case further development on and below level 9 will 
discover another “basalt’’-filled fissure more nearly in the general north-south 
line of the dike as known on the upper levels. 
