MINES OF RHYOLITE MOUNTAIN. 
279 
fissures of this zone are more widely spaced than the other, the whole zone being 
at least 30 feet in width. The ore occurs in the vicinity of the intersection of these 
two sets of fissures with a so-called “fiat vein” striking northwest and dipping 
northeast at 45° or 50°. This fiat vein is about 4 inches wide and consists of quartz, 
valencianite, and pyrite, these minerals apparently being a product of replacement 
of the surrounding rock. The pay shoot, so far as developed at the time of visit, 
follows this “fiat vein,” though the latter itself does not contain ore. The ore 
body as stoped in January, 1904, was about 60 feet long and from 6 to 20 feet wide. 
About 150 feet southwest of this place, or 200 feet southwest of the shaft, is 
another pay shoot known as the Arcadia shoot. This is an irregular chimney-like 
body of ore which has been stoped on all the levels. It occurs at the intersection 
of at least three nearly vertical fissure zones—one striking northwest, another 
north-northwest, and another northeast. According to the manager, Mr. Walter 
Swanson, these vertical fissures are crossed by a number of nearly horizontal fissures. 
The best ore occurs near these horizontal fissures. This ore body was lately reached 
by crosscutting on level 3. 
UNDERGROUND WATER. 
Water was first encountered in the Abe Lincoln shaft at a depth of 128 feet, or 
about 9,483 feet above sea level. The maximum flow of 500 gallons per minute 
was reached at a depth of 350 feet, but the Ophelia and Standard tunnels ultimately 
drained the mine. In sinking the shaft to level 3, in the winter of 1903, a little 
water was encountered near the new level, but this soon disappeared, probably as 
a result of the drainage by the El Paso tunnel. 
RHYOLITE MOUNTAIN. 
GEOLOGICAL FEATURES. 
Rhyolite Mountain, with an elevation of 10,771 feet, lies 2\ miles north of 
Cripple Creek and is separated from Mineral Hill by the deep trench of Spring Creek 
On its eastern side the Pikes Peak granite reaches nearly to the summit, but the 
western and northern slopes are covered by a volcanic breccia, with usually coarse 
fragments of brownish or dark-gray color. As a rule, it contains but little pyrite. 
A smaller area of breccia covers the southern slope of the adjacent Copper Mountain. 
It is similar in character, hut contains many large fragments of granite. There is 
some evidence that the breccia of Rhyolite Mountain is of local origin and formed 
in a volcanic neck underneath the summit. Several large and irregular areas of 
normal phonolite cover the southern slope of the hills and also occupy their summits. 
These masses of phonolite are in most places bordered by intrusive contacts. 
PROSPECTS ON RHYOLITE MOUNTAIN. 
At the eastern foot of the steep granitic slope of Rhyolite Mountain the Pay 
Rock claim is located. A shaft 80 feet deep was here sunk on a seam trending 
northwest and containing a little calaverite. The shaft was deepened to 300 feet, 
but, it is stated, without results. 
About 150 feet below the summit are the prospecting shafts of the Rhyolite 
Beacon Gold Mining Company, from many of which good assays are reported. In 
