196 GEOLOGY OF ASPEN MINING DISTRICT, COLORADO. 
The section PI. XLII, C, which passes through the Bushwhacker, also 
passes through the Park-Regent higher up. Near the upper part of the 
section the ore which was found in the Thompson stopes is seen resting 
on the Della fault and running up until cut off by the glacial drift. The 
occurrence of the other chief ore bodies in the mine is also shown, slightly 
generalized. Pl. XLIII, A, is a section of the northern end of the mine, 
taken through the Iowa shaft and the Iowa incline. The ore along this 
plane of section occurs, as usual, at the intersection of slight faults with the. 
Silver fault. The upper shoot shown is that which lies at the point where 
the two main Bushwhacker shoots come together. The lower shoots are 
developed at the intersection of the Regent system of slight faults with 
the Silver fault, and show the ore as occurring im the dolomite and along 
the Silver fault at these intersections. The fractures of the Regent system 
are cut obliquely by the plane of this section. 
MINERAL FARM MINE. 
The Mineral Farm mine shows essentially the same peculiarities as its 
neighbors. Ore occurs in the immediate vicinity of the Silver fault, some- 
times in the dolomite and sometimes in the breccia above. It follows 
certain nearly continuous north-south shoots, which probably mark some 
slight displacement or fracture. The ore is very high in baryta, the average 
being nearly 50 per cent. There is very little lead. Much of the barite 
is entirely barren of values, and from its nature seems to be a filling of 
preexisting fissures or cavities. These veins are often 2 or 3 to 10 or 12 
feet thick. 
ALTA ARGENT MINE. 
The Alta Argent mine was the northernmost working mine along the 
Cowenhoven tunnel at the time of examination. The tunnel runs from the 
Mineral Farm into the Alta Argent in Leadville dolomite, with the Silver 
fault close by on the west side. It soon encounters a fault which runs 
directly across the tunnel, and is probably nearly vertical, having an offset 
to the west on the north side of 20 or 30 feet. A short distance farther on 
another fault is encountered, having a similar displacement, and between 
these are vertical open fractures and watercourses, which increase in number 
toward the north. The maximum amount of fracturing is encountered still 
farther north, where in a space 30 or 40 feet wide the watercourses are 
