UNITED STATES, CANADA AND MEXICO 57
consists
in building large fires against the base of the rock which becomes
heated, whereupon water is thrown over it. The sudden change of
temperature cracks off large pieces, and much of the turquoise is
ruined in the process. After cracking off the rock, the turquoise is
picked out of the exposed seams with pieces of pointed iron, such as
old harrow-teeth, or any other sharp-pointed instrument. Only
occasionally is there a blast put in. The turquoise is sold in Santa
Fe, or along the line of the railroad in the vicinity of the mines, by
the Indians of the San Domingo pueblo, N. M. The specimens are ground
into round or heart-shaped ornaments, which are pierced with a crude
form of bow-drill, called by them " malakates." The drilling point is
either quartz or agate, and the wheel to give velocity was in one
instance made of the bottom of a cup. The selling price of the
ornaments is now very low, the Indians disposing of their specimens at
the rate of twenty-five cents for the contents of a mouth, where they
usually carry them. A string made up of many hundreds of stones, they
value at the price of a pony. Comparatively little of the American
turquoise finds sale except as cabinet specimens, or as mementos of
travel. Still, for ornamental or inlaying work, were it properly
introduced, it might have a large sale, as the green and blue-green
tints would contrast favorably with many stones or with dark wood. It
is possible that deeper workings will develop finer stones, perhaps of
such material as will maintain a more permanent color. Concerning the
origin of the turquoise veiningrock, both Prof. John S. Newberry and
Prof. Benjamin Silliman, Jr., regard it as eruptive. According to Prof.
Frank W. Clarke, the very small size of the veins and their limited
distribution show that the turquoise is of local origin, and he
emphasizes the idea that it has resulted from the alteration of some
other mineral. In addition to the facts tending to show its derivation
from apatite, there is also the fact that epidote containing lime is
present as a secondary product. The existence of the pyrite in the
gold-bearing veins may have had something to do with initiating the
process of alteration, and the alumina of the turquoise was probably
derived from decomposing feldspar. During the summer of 1885 a very full suite of specimens was collected by Maj. John W. Powell, and placed for analysis in the
