106 ECONOMIC GEOLOGY OF SILVERTON QUADRANGLE, [bull. 182. 
which may be considered as established and which bear directly upon 
the problem. No solution can be considered as satisfactory which 
does not take them into account. They will therefore be briefly sum- 
marized. 
The greater number of the productive ore bodies in the Red Moun- 
tain district, such as the Congress, Hudson, Yankee Girl, Guston, and 
Silver Bell, lie on or close to a line bearing about N. 21° E., which is 
probably a line of dominant fracturing. It is very probable, if not 
demonstrable, that a second nearly parallel zone of fractures extends 
through the ground of the National Belle mine southwesterly, past 
Summit and down Mineral Creek, to the Silver Ledge mine, near 
Chattanooga. The general course of this line is N. 30° E. The ore 
spaces are more or less irregularly spindle-shaped or ellipsoidal, with 
the longest axis commonly nearly vertical. The country rock in 
the vicinity of the ore spaces is usually much, and rather irregularly, 
fissured. Neighboring ore bodies are commonly connected by fissures, 
and this fact was taken advantage of in prospecting. When the ore 
spaces are elongated or elliptical in plan, the longer axis generally, 
although not always, lies a little east of north. In the Guston claim 
the ore spaces usually occur in wdiat is called the "ore break," a zone 
of fissured country rock striking N. 20° or 30° E. Similar "ore 
breaks" were recognized in the Genesee-Vanderbilt and in other 
mines. The country rock adjacent to the ore spaces is much altered, 
as described under metamorphism, pages 124-131, and is often thickly 
impregnated with fine pyrite. Mr. S. F. Emmons has recorded what 
seemed to him to be undoubted replacement of country rock, espe- 
cially of the Silverton breccia, by ore, and even the limited observa- 
tions now possible show that some replacement undoubtedly took 
place in both the Yankee Girl and Guston mines. 
It is believed that the explanation most consistent with the facts 
above stated and with others presented in the detailed descriptions of 
the mines is that the ore spaces were formed primarily by complex, 
intersecting Assuring, and were enlarged both by solution and by 
metasomatic replacement. The dominant Assuring seems to have 
been in a direction between 20° and 30° E. of N., and is well shown 
along two principal zones. But there was also much minor fractur- 
ing in various other directions. At the intersections of two or more 
of these fissures the country rock was usually brecciated and fur- 
nished channels for the ascending currents of warm or hot mineral- 
bearing waters which effected the pronounced hydrothermal meta- 
morphism so conspicuous in the rocks of this particular district. 
That such waters were capable of considerably enlarging the irregulai 
conduits through which they circulated, either prior to or during tin 
deposition of the ore, seems likely when the shape of the ore spaces 
and the extent to which the rocks in their vicinity have been altere( 
are taken into account. It must be admitted, however, that in the case 
