and
masses, but veinlets of turquoise of good color as much as one-half
inch thick have been found. Excellent matrix turquoise has formed where
the brown limonite stains have penetrated and filled seams and
interspaces in turquoise veinlets and segregations. Such matrix, when
cut, would present beautiful contrasts of fine blue and brown with a
variety of patterns and markings. Little pure turquoise has been
removed since the last regular mining a number of years ago. Some
matrix containing bright-blue turquoise in brown iron-stained rock has
been encountered in exploration during recent assessment.
Of
the many excavations at and around the old Castilian mine, those of the
ancients were probably more extensive than the recent ones. The extent
and nature of much of the ancient work has been concealed by caving and
other agencies of time and by modern work in the same places. Large
pitlike depressions and many smaller openings mark some of the ancient
work. Numerous prospect pits, trenches, and shafts have been made in
recent times. As would be expected little turquoise was left in sight
from the last work, and since the deeper workings were not opened
little could be learned of the nature of the deposits.
The
rock at the Castilian mine is quite similar in appearance to that at
the Tiffany mine and may be called monzonite porphyry. Alteration has
been extensive and the resemblance of the decomposed rock at each mine
is striking. A thin section of the altered rock from one of the shafts
at the Castilian mine contained phenocrysts of plagio-clase and
orthoclase with a groundmass of lath-shaped feldspar crystals with
partial trachytoid texture. Other minerals were
E
lentiful, pyrite
crystals, magnetite, apatite, and a few shreds of pale rown biotite,
much secondary epidote and calcite. Less altered phases of the
monzonite porphyry outcropped in places near the mine workings.
From
the nature of the work and the type of rock encountered it is probable
that the occurrence of turquoise at the Castilian and surrounding
claims is similar to that at the Tiffany mine. Several lines of
prospects and open cuts have been made in a northeast-southwest
direction and other workings also indicate leads of turquoise with a
northwest trend. Some good turquoise has been found in the Castilian
mine, but a larger proportion is reported to have a greenish-blue shade
than at the Tiffany mine.
Other
claims have been located east of the Tiffany mine and on the northeast
side of the main hill by Mr. McNulty and others. Some of these are
reported to carry also copper and gold. A little greenish-blue
turquoise has been found in seams and nuggets or nodules in a few of
these claims.
CALIFORNIA.
Turquoise
has been mined in the northeastern part of San Bernardino County,
Cal., by the Toltec Gem Mining Co. and the Himalaya Mining Co., both of
New York. These companies have not operated their mines for several
years, the Himalaya Mining Co. having closed down in 1903. The Toltec
Gem Mining Co. owns three groups of claims known as East Camp, Middle
Camp, and West Camp. In a letter from Mr. C. F. Lamont, of New York,
treasurer, East Camp is described as 50 miles from Manvel, Middle Camp
5 miles from East
