Sangre de Cristo Mountains on the east and the Continental Divide on
the west. The southern portion, say seventy-five miles in lineal
(northerly and southerly) extent, has been extensively denuded. The
more northerly area has been eroded more or less, and contains
accumulations of gravel, varying from fifty to six hundred feet in
depth. Overflows of volcanic rocks cover and protect or interstratify
the gravels in very many instances. The gravel consists chiefly of
quartz and quartzite, and, to a much less extent, of syenite, porphyry,
granite, gneiss, and slate debris, and evidently has been carried to
its present location from only a short distance, probably from the
Archaean rocks of the Sangre de Cristo and other southerly ranges of
the Rocky Mountains. The gold is said to be diffused through the
alluvions with great uniformity.
of Santa Fe large Mexican grants contain extensive deposits of gravel,
where gold was discovered in 1842, and whence in succeeding years large
amounts of the precious metal are said to have been extracted.
American companies have been recently formed to work all these
deposits along the Rio Grande, but thus far the obstacles to success
seem to have been very great.
Other States and Territories.—In
various other States and Territories, as Colorado and Dakota,
placer-mining has been carried on by small companies on a limited