Record of Geology op Texas, 1887-1 896. 
53 
Cummins^ W. F. 
iG. H. & 'S. A. R. R. iThe iDiaboIo 'Mountain district is about one hundred 
and twenty-five miles east of El Paso- There are some other localities in 
the county where there has been considerable prospecting done, and where 
there will be found valuable properties no doubt, but for the present 
nothing is being done to develop them. The Quitman district so far has 
produced principally argentiferous galena; occasionally gold has been 
found, but not in paying quantities. The mineral generally occurs in 
veins traversing the country rocks. These veins are from a few inches to 
several feet in width. The country rock is usually granite or porphyry. 
The lower foothills are Cretaceous limestone. The vein material is some- 
times quartz, sometimes carbonate of lime, and in other places it is car- 
bonate of iron. There are some good veins of mineral in contact veins. 
These contacts are between porphyry and limestone. The highest moun- 
tains are composed of igneous rocks, while the limestones are at the base 
of the miounjtains and dip at various angles, according to their proximity to 
or remoteness from the general line of upheaval. The limestones on the 
north side of the mountains belong to the 'Cretaceous formation. Elsewhere 
I did not examine them sufficiently to determine their geological age. 
. ****«■•» -JC- 
“The other district I have mentioned, the Diabolo, is about eight miles 
north of the line of the T. & P. R. R. The most of the ore taken from 
that district has been shipped from Carrizo 'Stationj The ores of this dis- 
trict are copper and silver- No galena, so far as I know, having been 
found here. The ore occurs in well defined fissure veins, and in contacts. 
'The veins are found traversing the country rock almost perpendicularly 
in a northeast and southwest course. The country rock is a fine grained 
red argillaceous sandstone, massive, showing no lines of stratification, 
breaking with conchoidal fracture, and much broken up by atmospheric 
influences. It has no fossils. It is overlaid by the rocks of the Carbon- 
iferous formation, but never having seen any of the underlying strata, I 
have been unable to determine to what geological formation this red sand- 
stone belongs. The copper ores are gray copper ( tetrahedrite) , copper 
pyrites, malachite, and azurite. These ores all carry more or less silver. 
In the gray copper ores the silver is native, and yields a very large, per 
cent.” 
The OarboniferoTis Form'atioii in Texas. 
Geol. and Scientific Bulletin, Vol. I, Ko. 3. Houston, July, 
1888. 
Extract: “I have seen the Carboniferous rocks as far south as Marble 
Falls, in Rurnet county. The eastern boundary of this formation begins 
at a point on Red River, near the northeast corner of Montague county, 
thence through Wise county, crossing the Texas and Pacific Railroad near 
the town of Millsap, and thence in a southwestern direction to the iColor- 
ado river. The western boundary of the formation begins at a point on 
Red River, near the northwest corner of Montague county, thence south- 
westwardly, crossing the Texas and Pacific Railroad near iBafi’d, and 
thence to the Colorado river, near the town of Ballinger. This coal field 
