W. T. SchaUer— Dumortierite. 223 



Again assuming that his water content is somewhat high, 

 the ratios agree well with the new formula. 



This concludes the list of analyses of dumortierite which 

 were made on pure material and with due knowledge of what 

 was to be determined. A number of other analyses will now 

 be given which serve in a general way for the determination 

 of the composition of the mineral, but can not be relied on 

 for exact results. 



One, which has heretofore not been published, was made 

 by the writer on the Washington dumortierite. About 200 

 grams of the rock was powdered and by repeated separation 

 with heavy solutions about 4 grams of dumortierite were 

 obtained. The sample was by no means pure. It was found 

 impossible to remove all the andalusite, an unknown but small 

 amount remaining. It was found during the course of the 

 analysis that the sample also contained some titanite (leucoxene) 

 and a very small amount of pyrite. The analysis was made 

 with all the care possible and the following results were 

 obtained : 



Ratios after deducing titanite. 



SO 



28-51 



5*97 



7-80 



1-53 

 1-03 



or 6 X "99 



A1.0,— -- 



Fe.O, 



TiO, 



HO ...... 



59-75 



2-48 



-95 



2-12 



8 X '97 

 1 X 1'53 



BO 



._.. 5*54 



1 X 1*03 



- J -'2 3 



CaO 



-68 





100-03 

 Excepting for the high-water content, the analysis agrees 

 very well with the formula. No allowance was made for the 

 small amount of andalusite present, which would slightly alter 

 the ratios. 



There now remain the analyses of Whitfield and Riggs, of 

 which but one is suitable for any calculation. The analyses 

 are as follows, No. 1 being of the New York mineral, by 

 Eiggs, No. 2 of the New York, and Nos. 3 and 4 of the Ari- 

 zona mineral, by Whitfield : 



12 3 4 



Si0 2 34-82 31-44 31*52 27'99 



A1 2 3 55-30 68-91 63'66 64-49 



MgO°._ -57 -52 tr. 



K 2 1-04 -11 



Na„0 . 1-76 .... -37 



PA - --- ---- --- '20 



B 2 3 4-07 tr. 2-62 4-95 



lorn 2-96 1-34 1*72 



100-52 100-35 100-14 99'35 



