146 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
this district has undergone that it seems both the minute fractures and the 
larger faults must have resulted from the same cause. In closely folded 
regions it has already been demonstrated that the slight wrinkles or flutings 
in rocks have an intimate connection with the more important system of 
folding, and may often be used in deciphering this system. On studying 
the fracture planes in the specimen figured, and in other specimens from 
the same locality, the conclusion is forced upon one that this finer structure 
may be taken, in a guarded way, as indicative of the more general system 
of fracturing and of faulting on a larger scale. Almost every feature con- 
nected with the fracturing in this specimen (and they can not all be well 
seen in the reproduction) finds its parallel in the peculiar system of fault- 
ing in Tourtelotte Park. The different blocks which these fractures make 
by intersection have been brought into relief by shght weathering, which 
has removed more iron from certain blocks than from others, and so 
produced a difference of coloring, which brings out the structure strikingly. 
Careful observation will show that there are not only different systems of 
fracture in this specimen, but movements of Citerem ages, for some of 
them have slightly faulted others. 
Mineralization —Immediately following this faulting and fracturing at the 
beginning of the uplift came ore deposition. Ores are now universally 
found along these faults and fractures, either in vertical faults or, more 
commonly, at the contact of vertical ones with those which are parallel to 
the bedding. The ore was deposited as sulphide, and the mineral-bearing 
solutions evidently: circulated along the channels which the faults and frac- 
tures offered. The epoch of ore deposition was short compared with that 
of the faulting, for we know that the faulting has heen continuous, and can 
trace several distinct systems which have developed successively from the 
earliest period to the present. The first-formed systems are ore bearing, 
showing that they existed at the time of the presence of the mineral-bearing 
solutions. The later systems are, however, barren, and evidently no ore- 
bearing waters have circulated along them. ‘This refers, of course, to the 
main or primary mineralization. There is always going on a secondary 
deposition of ore, due to the rearrangement of the first-deposited minerals, 
but this process is comparatively unimportant. 
Fault systems.—After the formation of the first or north-south system of 
faults, which we may call the Aspen Mountain system, the next in point 
of age was the Della system. These faults are not numerous, and have no 
