Allen and Clement — Role of Water in Tremolite. 107 



Table III. 



■Total Loss at Different Temperatures. 

 (Ham Island, Alaska). 



Tremolite 



Grams 

 taken 



Time 



Temper- 

 ature 



Loss 



Percentage 

 loss 



Per cent of 

 total water 



2 



lOf brs. 

 10^ " 



500° 



750° 



6-7 



8-5 



mg. 



•33 

 •42 



14-5 



18-3 





n " 



805° 



8-7 



it 



•43 



18-8 





11 



845-850° 



9-1 



u 



•45 



19-6 





26 " 



863° 



10-4 



a 



•52 



22-5 





7 " 



875° 



10-9 



a 



•54 



23-4 





15 



890° 



12 -2 



a 



•61 



26-3 





15 



918-920° 



14-4 



a 



•72 



31'1 





32 " 



930-933° 



22-1 



a 



1-10 



47-7 





Proportional j 

 loss for 2 gr. [ 



5 



8* 



u 



200° 



10-9 



a 



4-4 



•22 



9-5 





81 



it 



300° 



13-0 



a 



5'2 



•26 



11-2 





10 



u 



400° 



15-5 



a 



6'2 



•31 



13-4 





12* 



u 



500° 



17'3 



u 



6-9 



•35 



14-9 





13| 



it. 



600° 



20-4 



(i 



8-2 



•41 



17-7. 





n 



a 



725° 



21-8 



it 



8*7 



•43 



18-8 





H 



u 



800° 



22-5 



11 



9-0 



•45 



19-4 





10 



u 



915° 



34-2 



tl 



13-7 



•68 



29-6 



about 



100 



it 



960° 



1158 



It 



46-3 



2-31 



100-0 



Interpretation of the curves. — It will be seen that all the 

 curves (fig. 3) rise very slowly and in nearly a straight line 

 until a point approximating 850° is reached, when they bend 

 strongly upward. The point seems to vary somewhat with 

 the composition of the mineral. The curves appear to be 

 smooth ; still one might suspect that so strong a change in cur- 

 vature indicated some abrupt change in the physical or chemi- 

 cal condition of the mineral. The microscopic evidence shows, 

 however, that the crystal form, with such optical properties as 

 can be quantitatively measured — extinction angle, index of 

 refraction — remain almost unchanged. In the purer specimens 

 from Ham Island and Ossining, and in that from Gouverneur. 

 there is no essential difference between the mineral before and 

 after heating, except in the development of bubbles through- 

 out the mass, which increase in number as more water is lost. 

 In the Edwards specimen, a beautiful parting parallel to the 

 base continued exactly as it was before heating. There is a 

 change in the color of the specimen from pink to dull green- 

 ish, which is probably due to the absorption of oxygen by the 

 manganese oxide, 1-28 per cent of which is present. This, 

 however, has nothing to do with the bend in the curve, for 

 the color change was just as noticeable in a portion of the min- 



