CHAPTER VI. 
DESCRIPTION OF THE IRON ORES. 
DISTRIBUTION, EXPOSURES, ANT) TOPOGRAPHY. 
The iron ores occur in disconnected masses within a general area 
about 1J miles wide by 20 miles long, running northeast and south- 
west through the district mapped. (See Pis. II, XV, XVI.) They 
lie for the most part on eastern and southern slopes or foothills of 
The Three Peaks, Granite Mountain, and Iron Mountain, between 
elevations of 5,600 and 6,700 feet, but some of them, as on Iron Moun- 
tain, appear at or near the tops of the mountains at elevations between 
7,000 and 8,000 feet. 
Some of the iron-ore exposures stand out as much as 200 feet above 
the surrounding country as black, jagged ridges (Pis. XVII, B, to 
XIX, A). Others, including several of the larger deposits on the lower 
slopes, do not stand above the surrounding rocks (PI. XIX, B), but 
are known by isolated exposures and black iron-formation fragments 
disseminated in the loose detrital material at the surface. Some of 
the ore does not appear at the surface at all, being covered by andesite 
detritus washed from the upper slopes, though, even here, fragments 
of ore are likely to appear in the detritus farther down the slopes. 
In such places the exact shape and distribution of the deposits can 
not be determined without trenching or pitting. Fortunately such 
work will suffice fairly well throughout the possible ore-bearing areas, 
though there are places where areal extensions of iron-ore belts may 
be found by underground exploration, or where belts, mapped as 
continuous on the basis of the surface fragments, may really be dis- 
continuous. The deepest pits in the district, 130 feet, have not yet 
reached water level. 
GEOLOGICAL, AND STRUCTURAL RELATIONS OF THE ORE 
DEPOSITS. 
The ore deposits for the most part lie at or near the contact of the 
andesite laccoliths and the Ilomestake limestone. Some of them 
occur entirely within the andesite well up the slopes, and others 
entirely within the limestone, but seldom far from the contact. (See 
Pis. III-V, pocket.) 
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