PROCEEDINGS OF THE NATIONAL, MUSEUM, 

 Comparhon of Jadeites from Burma and America. 



VOL. 60. 



Si02. 

 MgO. 

 CaO. 

 Na^O 



58.83 

 0.78 

 1.08 



14.40 



58.23 

 2.65 

 4.02 



10.06 



The difference is obvious. Of the American jadeites only 4, or 

 about 33 per cent, show compositions that are closely similar to those 

 of Burma. This is a subject which it is hoped to study soon in con- 

 nection with some large collections of jades from Middle America. 



Consideration of the densities of jadeites leads also to the sugges- 

 tion of the possibility of the existence of a definite, equimolecular 

 mixture of jadeite and diopside, possibly much as dolomite is related 

 to calcite and magnesite. In a discussion of the densities of the jade- 

 ites of the Bishop collection, Hallock" shows that the average of 107 

 jadeites (including a few chloromelanites) is 3.3202. He then gives 

 the following table of grouped averages, from which the chloromel- 

 anites are omitted: 



43 jadeites average 3. 3351 



27 jadeites average 3. 3252 



8 jadeites average 3. 3182 



4 jadeites average 3. 3041 



19 jadeites average 3. 2517 



The average densities are clustered at either end. Using the figures 

 given, if weights are assigned to the two heaviest and most numerous 

 average densities according to the number of determinations, com- 

 bining them we arrive at the result: 



70 jadeites of average density 3. 331 



19 jadeites of average density 3. 252 



Between these there occur only 12 jadeites, with a wide interval be- 

 tween them and those of lowest density. These figures, so far as 

 they go, would seem to mdicate that archaeological "jadeite " is mostly 

 the pure soda jadeite, and that a fairly definite diopside-jadeite also 

 occurs quite abundantly, but that there are comparatively few inter- 

 mediate members of the series. 



Because of the intermediate position of the Tuxtla diopside-jadeite 

 it will be of interest to state succinctly the correlation of some of the 

 properties of it and of the end members of the series. The data for 

 soda jadeite were determined by Merwin on the two small crystals 

 isolated by Penfield from the material the analysis of which is given 



» W. Hallock. In H. R. Bishop's Jade Book, vol, 1, p. 116, 1906. 



