CHEMICAL ANALYSES 



469 



This determination as mesolite was based on a carefully made chemical 

 analysis, which apparently closety coincided with analyses of undoubted 

 thomsonite from Table mountain and elsewhere; but inasmuch as Cross 

 and Hillebrand had published analyses of an apparently identical 

 mineral from Table mountain, and had determined the mineral to be 

 mesolite, it seemed advisable to submit the material in question to a 

 renewed investigation. The result showed that the material used for 

 the first analysis was not absolutely pure, but contained just enough 

 carbonate of calcium to make the analysis closely approximate that of 

 thomsonite. The material on which the later analysis was made was 

 obtained at a later date and proved to be perfectly pure. 



Chemical Analyses 



The chemical analyses given below were carried out in the chemical 

 laboratories of the Colorado State School of Mines. Analyses 1 and 2 

 were made by President Regis Chauvenet, and number 3 by Doctor 

 Robert N. Hartmann. In presenting these analyses the author wishes 

 herewith to acknowledge gratefully the valuable assistance thus ren- 

 dered. In all three cases great care was exercised to secure absolutely 

 pure material. Number 1 was taken from thomsonite of type II and 

 was obtained by carefully breaking off the freely projecting needles and 

 prisms. Number 2 was taken from the center of a mass some 2 inches 

 in diameter and represents thomsonite of type III. Number 3 repre- 

 sents a fine cotton-like mass of mesolite. For purposes of comparison, 

 five analyses are also given which were made by W. F. Hillebrand* 

 from material collected by the U. S. Geological Survey from Table moun- 

 tain. Judging from the descriptions accompanying these analyses, IX 

 and X represent thomsonite of type I, while XI and XII represent 

 either type II or type III. Number XVIII is mesolite. 





Num- 

 ber 1. 



Num- 

 ber 2. 



Num- 

 ber 3. 



IX. 



X. 



XI. 



XII. 



XVIII. 



Si0 2 



41.34 



41.59 



45.59 



40.88 



40.68 



41.21 



42.66 



46.17 



A1A 



30.35 



30.59 



25.18 



• 29.68 



30.12 



29.71 



29.25 



26.88 



CaO 



11.20 



11.15 



8.93 



11.88 



11.92 



11.34 



10.90 



8.77 



Na 2 



5.04 



4.66 



7.65 



4.72 



4.44 



5.62 



4.92 



6.19 



H 2 



12.27 



12.24 



12.67 



12.91 

 100.07 



12.86 



12.20 



12.28 



12.16 





100.20 



100.23 



100.02 



100.02 



100.08 



100.01 



100.17 



* Bull. No. 20, U. S. Geol. Survey, pp. 25, 35. 

 LXVII— Bum,. Geoi,. Soc. Am., Vol. 11, 1899 



