70 IRON ORES OF IRON SPRINGS DISTRICT, UTAH. 
Marshall, Blowout, Dexter, and Pot Metal claims. At the Desert 
Mound a fault breccia crosses andesite, ore, and limestone, and mag- 
netite constitutes breccia fragments. 
The iron ores lack the associated "iron formation' 7 of ferruginous 
chert or jasper so characteristic of the Lake Superior iron ranges. 
The nearest approach to jasper is in ores banded parallel to the walls 
in the fissure veins in the andesite, and in contact ores with a banding 
representing original limestone bedding. 
The ore deposits nowhere come in contact with the later efTusives. 
However, it is a significant fact, to which attention will be directed in 
discussion of origin of the ores, that the principal ore deposits are 
approximately on the level of the general surface upon which the 
lavas rest, sometimes above it but never below, and that the effusive 
rocks before erosion must have rested upon the present deposits. 
(See fig. 9.) 
KINDS AND GRADES OF ORE. 
The following description applies to the ores as they appear above 
water level. Pits have not yet been sunk below this depth. 
The ore is mainly magnetite and hematite, usually Ultimately 
intermixed, but locally segregated. So far as present information 
goes (and it does not go far below the surface) the magnetite con- 
stitutes about 70 per cent and the hematite 30 per cent of the whole. 
As hematite appears more abundantly below the surface, it is thought 
likely that deeper exploration will develop a higher percentage of 
hematite. At the surface the ore is ordinarily hard crystalline mag- 
netite and hematite in porous, gnarled, and contorted masses, with 
coarsely crystallized quartz and fibrous chalcedony as the principal 
gangue mineral, filling, wholly or partly, cavities in the ore. Other 
gangue minerals occurring in small and practically negligible amounts 
are apatite, mica, siderite, diopside, garnet, pyrite, chlorite, calcite, 
barite, galena, amphibole, copper carbonates, limonite, and amethyst. 
Of these minerals barite and galena are more closely associated with 
the limestone than with the ore. Melanterite, associated with pyrite, 
was found in process of formation in the long tunnel on the Duncan 
claim. Beneath the surface the ore is usually softer and contains a 
larger proportion of soft, bluish, reddish, brownish, grayish, and 
greenish banded hematite, limonite, and magnetite in greatly varying 
proportions and relations. The gangue materials are more abundant 
than near the surface, and calcite is in relatively increased proportion 
as compared with the quartz. The banding in the contact ores 
partly represents the bedding of the limestone, which, as will be 
shown later, the ore replaces. Banding in the dike or vein ores in 
the andesite is of unknown origin, possibly the result of original 
deposition. Some of the softer ore at lower levels entirely lacks 
this banding. Locally, as on the west side of Lindsay Hill, the 
