2C2 
Transaction's Texas Academy of Science. 
Streeruwitz, W. H. Von. 
found, however, resembling those of the Quitman.s. The surface rock of the 
Sierra iBlanca Mountains consists of a quartzitic umterial in sharp, angu- 
lar fragments, varying in size from six inches to more than six feet, evi- 
dently a metamorphic or .semifused sandstone, with occasionally a thin layer 
of crysitals of hornblende. These quartzites, which are broken at nearly 
right angles to the plane of the original stratification, are devoid of petre- 
faetions or impressions of organic matter. They evidently cover the slopes 
and summits to considerable depth, coinciding in their present inclination 
with the mountain slopes. The isolation, character, and peculiar shape 
of the Sierra Blanca Mountains seem to point to laccolitic intrusions as 
their origin. 
■“The four mountain cones of this group are decidedly newer than the 
Lower Cretaceous rooks surrounding them. The dip of the Lower Creta- 
ceous hills in the vicinity of the Sierra Blanca Mountains is the same as 
that of the quartzite forming the slopes of these mountains, and the saddle 
of Lower Cretaceous limestone, with excellently preserved specimens of 
fossils, lying between two of the mountains, and stratified horizontaliy, 
seems to indicate that the upheaval of all the mountains of this group 
took place simultaneously and prcubably gradually after its deposition. 
“From observations made up to this time no connection can be found 
between the intrusive material of the Sierra Blanca cones and the eruptive 
rocks of the nearest or northwestern ridge of the Quitman Mountains, and 
it will require careful study and comparison with the Quitman Mountains, 
and the distant ranges and groups to the northward, to justify final con- 
clusions. 
“The foothills east and south are Lower Cretaceous, with numerous and 
extensive porphyritic intrusions. To the west there are more recent 
( Quateniary ? ) beds, sloping gently towards the river and intersected by 
numerous ravines and dry watercourses. The Sierra Blanca Mountains, 
with their fragment-covered surface, and the foothills west of them, show 
fewer distinct ore outcrops, and are lacking in the tempting indications 
of ore deposits and veins found in the Quitmans and their foothills. I 
regard this plainly visible presence of ore in the Quitman Mountains, and 
the absence of such distinct indications in the Sierra Blanca group, as an 
additional evidence that they belong to separate upheavals, independent 
of each other, and also of the laccolitic character of the Bierra Blanca 
group.” iPp. 219-220. 
“In the Quitman Mountains, the Bonanza and Alice Ray mines have 
shipped some good ores, containing 30 per cent, and over of lead, 25 to 30 
per cent, of zinc, with from 20 to 30 ounces of silver, and traces of gold — 
say an average value of $60 to $65 per ton; * * .” P. 223. 
369. 
Report of. 
Second Ann. Rept. of the Geol. Surv. of Texas, 1890, pp. xci- 
xciv. Austin, 1891. 
An administrative report. It deals witli the difficulties of carrying on 
geological work in the Trans-Pecos region on account of the scarcity of 
