many
seams of quartz. The granite porphyry is cut by two or more dikes of
fine-grained dense white porphyry or aplite. These do not appear to
bear any relation to the deposition of the turquoise, however. An open
cut at this mine was made in the end of the ridge in a very rugged rock
outcrop. Some good turquoise is reported to have been found here,
though the streaks of gem failed or were not successfully followed in
the workings. At the two openings about a hundred yards to the east
some very good grade turquoise and large lumps of off-colored green
turquoise were found. These occur in veinlets and seams through the
granite porphyry and with the quartz seams.
John
Caswell of Mineral Park owns a claim with a turquoise deposit in the
cliffs and at their foot in the knob at the west end of Ithaca Peak.
This claim was not visited, though promising specimens of turquoise
matrix were seen that had been obtained during assessment-work on the
claim.
The
claims of Mrs. John Kay are on the slopes below the cliffs on the
southwest side of Ithaca Peak and beloAv the Monte Cristo claim of the
Aztec Company. These claims were not examined, though considerable
turquoise matrix is reported to have been mined. Almon Stone, of Los
Angeles, Cal., reports a specimen of matrix weighing 34 pounds from
this mine. The estimated value for this rough lump was $50. The bulk of
the matrix is valued at $1 to $5 a pound.
COLORADO.
The
mine of the Colorado Turquoise Mining Company consists of ten claims
situated 13 miles S. 60° E. of La Jara, Conejos County. Ancient
workings are reported to have been found on the outcrop of the
turquoise, with a few antique stone implements around them. The mine is
in a low hill among the group of small hills in the mesa country about
1-1/2 miles west of the Rio Grande.
The
higher hills west of the mine are capped and partly composed of beds of
basaltic rock. The turquoise is associated with a partly decomposed
trachytic rock which in places bears quartz or is quartz porphyry. This
rock is a dense, very fine-grained white rock, composed chiefly of
feldspar. Secondary scricite and kaolin are present. Much of the
trachyte is badly stained with brown limonite not only along joints and
seams but through the rock, often in concentric layers or shells. This
feature is very like that at the old turquoise mine on Mount
Chalchuitl, near Cerrillos, N. Mex. In places kaolini-zation has been
very extensive, and nearly pure kaolin has resulted; in other places
small quantities of quartz are present, generally as phenocrysts. A
dike of fine-grained, dark-greenish to black rock, probably a variety
of phonolite, cuts across the trachyte in a northerly direction. The
crest of the hill or ridge in which the turquoise occurs is capped with
a ledge of dense-gray to light-brownish chert or hornstone, about 20
feet thick and outcropping in a direction N. 70° W. Diorite or andesite
outcrops to the east of the turquoise-bearing rock, part being on the
company's property.
The
turquoise occurs in seams and joints and occasionally in irregular
masses in the trachyte. The seams vary from paper thickness to over
one-quarter of an inch in thickness. The most prominent set of joints
bearing turquoise appear to strike north of east and have veinlets
branching from them in various directions. A small amount
