W. P. Blake on the Chalchihuitl of the Mexicans. 299 
On breaking open one of the dark green’ fragments a small 
cavity was found in the centre, like the interior of a geode, with 
the color gradually shading into white. The interior‘surface is ‘ 
smooth and finely mamillated, reminding one of the inner sur- 
face of nodules of chalcedony. There are not any distinct layers 
a8 in agate but the color gradually diminishes from the surface 
to the center. A variation in the amount of the coloring matter 
in different specimens according to the circumstances of forma: 
tion is thus indicated, and it is seen that the composition of the. 
mineral cannot be regarded as constant. This variation of color, 
and the structure, indicate an origin, or formation, similar to 
that of chalcedony and agate,—a deposition in thin layers from 
either a vapor or liquid. 
, There did not appear to be any principal vein or well defined 
deposit of the mineral; it is apparently distributed in thin seams 
srough a great body of the rock. It is possible that there is a 
large vein or seam covered from view by the debris. rock 
ering, and very much resembles a sandstone. Veins of copper 
be determine whether it was possi , oe 
nin part made for ores or the precious metals, but i . 
dent that the chalchihuitl was the only mineral which had been 
Sought for 
a The evident antiquity of this excavation, and its extent, ren- 
— It peculiarly interesting. Little or nothing appears to 
own of it in that region, and I am not aware that it has ever 
n visited except by the Indians and New Mexicans. It 
the Country by the Spaniards. It does not appear that anything 
‘ has en Sane in thei aba pit for a long time. This is shown 
- ae my by the pine trees growing in it, but by the i 
=e Sides, ‘and by the piles of rock, gray with age, gues ti 
Margin. F ragments of ancient Indian pottery can ei y 
My! - Che place is, however, occasiona 
b 
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