Vol.. 8, 1922 
PETROLOGY: H. S. WASHINGTON 
325 
of the two are separated by a dashed Hne, which extends from the diopside 
apex (on the basis of Bowen's experimental observation that typical diop- 
side is incapable of holding feldspar in solution), to a point on the Ab-Jd 
border, at about 80 Jd-20 Ab. Some other analyses might have been 
plotted, which harmonize with those shown. The straightness and exact 
position of the dividing line are somewhat conjectural, but more jades 
which appear to fall near it, are being studied chemically and optically, 
so as to determine its position more accurately. 
This series of rocks belongs evidently to the general group of jadeite 
jades, but differs from the usual jadeite of Burma and other sources of 
Chinese jade in two important particulars: the constant presence of 
large or considerable amounts of diopside with the jadeite in the pyroxene; 
and the presence of much albite in most of the series, either wholly in 
solid solution in the pyroxene, or partly so ("occult") and in part sepa- 
rately crystallized. The series, thus, extends from pure tuxtlite (diopside- 
jadeite, 1:1) to nearly pure albite. Further discussion of these points 
cannot be undertaken here, for lack of space ; but it is suggested that this 
series shows such well-marked general and serial characters as to be de- 
serving of a special name. That here proposed is mayaite which 
recalls the ancient nation who used and valued it, and which may distin- 
guish it from the more widely known Burmese jadeite jades (with little 
or no diopside or albite). Purely jadeite jade seems to be unknown 
from, or at least is of very rare occurrence in. Middle America. 
From these petrological considerations, the conclusion is inevitable that 
the material of the Central American and Mexican "jade" objects is of 
American and not Asian provenance. Although no American locality 
is yet known where mayaite occurs in situ, yet there are numerous 
specimens which are either clearly pebbles or show traces of pebble sur- 
faces. But this is not the place for archaeological discussion. It may 
only be said, in conclusion, that various considerations regarding the 
occurrence of igneous rocks in different parts of the North American 
continent, as well as of the occurrence of Middle American jade objects, 
lead me to the behef that: (1) the jades come unquestionably from either 
Mexico or from Central America, or from both, and that (2) there are prob- 
ably two centers of supply, both near the west (Pacific) coast, one probably 
in Oaxaca or Guerrero, and the other probably in Guatemala. 
1 The term "Middle America" is used to include both Mexico and Central America. 
2 H. S. Washington, Proc. U. S. Nat. Mus., 60, Art. 14, 1922. 
3 Clarke and Merrill, Proc. U. S. Nat. Mus., 11, 1888 (122, 124). 
* H. S. Washington, J. Wash. Acad. Sci., 12, 1922 (387). 
5 N. L. Bowen, Amer. J. Sci., 40, 1915 (161). 
