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PETROLOGY: H. S. WASHINGTON 
Proc. N. a. S. 
amount. It would seem, therefore, that the Hmit of solubility of albite 
(with a little anorthite) in diopside-jadeite is somewhat less than 20% 
by weight of the mixture. Further study of this somewhat interesting 
point is being undertaken. 
The normative mineral relations of the Middle American jades are shown 
in the accompanying figure 1, in which the apices are the points for 100% 
(by weight, not molecular) of albite (including anorthite), jadeite, and 
diopside; the loci are those of the specimens whose analyses are given in 
FIGURE 1 
Mineral composition of jades 
table I (except No. 13). There appears to be a marked tendency to 
cluster about the general composition: 70 jadeite, 10 diopside, 20 albite; 
and the greater number are strung along and rather near the albite- jadeite 
side. It is noteworthy that none of them fall on this border line, indicat- 
ing the constant presence of diopside; while two fall almost on the line of 
equal amounts of jadeite and diopside, and only one (the Copan pebble) 
falls well within the dominantly diopside-albite part of the triangle. 
In figure 1 the jades without visible feldspar are indicated by dots, while 
those with feldspar visible in the section are shown by crosses. The areas 
