20 
TRANSACTIONS OF THE TEXAS ACADEMY OF SCIENCE. 
gold or to some of the base metals, in ores as sulphide, chloride, chlo- 
robromide, telluride, etc., sometimes pure, but mostly in combina¬ 
tion with the ores of base metals, particularly with the ores of lead, 
copper, zinc, tin, antimony, with arsenides, etc. And though its dis¬ 
tribution is not as general as that of gold, it is found in larger quanti¬ 
ties in and with the ores of base metals. 
Though all these may be well known facts, I had to mention them, 
because one or the other point might assist me to demonstrate theo¬ 
retically the possibility and probability of the existence of precious 
metals in Texas. The same reason makes it advisable to mention 
some principles of mining geology, which principles are based on the 
experience of centuries. 
Ore deposits in general are more frequently found in older than in 
newer rocks. They more frequently exist in mountainous regions 
than in level countries, oftener in close proximity to eruptive rocks 
than farther removed from them, more frequently with older than 
newer eruptive material, and more frequently with and in plutonic 
than in volcanic rock. 
Ore deposits are indicated by direct outcrops of the ore, of quartz, 
carbon spars, barite, lluor spar, aragonite, mica, garnet and many other 
minerals, forming the gangue, among them particularly iron cappings, 
etc.; by peculiar discoloring and decomposition of tbe surface; by 
springs or moisture on the surface; by richer, poorer or peculiar vege¬ 
tation ; by float pieces, etc. 
Now, Central Texas, and more so the region between the Rio Grande 
and Pecos river, are mountainous, many peaks reaching the height of 
6000, 7000 and 8000 feet, “El Capitan,” in the Guadaloupe range, 
about 10,000 feet. 
The mountains of the Central district, as well as of Trans-Pecos 
Texas, belong to older and oldest geological formations. 
Older and newer eruptive rock prevails in the mountains of West 
Texas and appears over several thousand square miles in the Central 
district; or in short, the conditions favorable to ore deposits exist in 
the Central district (the center of which is Llano county) as well as in 
Trans-Pecos Texas. 
The mountain ranges in Colorado, Arizona, New and old Mexico are 
ore-bearing, as is proved by mines and prospects. They are built up 
of the same materials, and at least partly contemporaneous and under 
the same conditions as those of West Texas and the Central district, 
and the mountain ranges of West Texas at least are the continuations 
of the Mexican, New Mexican, Arizona and Colorado ranges through 
Texas. Gold is found in situ in older rocks—granites, gneissic rocks, 
schists and many others, and in their detritus. All these rocks occur 
frequently and very extensively in West Texas and the Central dis¬ 
trict, so their detritus. 
