192 JPenJield and Howe — Chemical Composition 



our investigation as it afforded abundant material for testing 

 the methods of the mechanical separation and the chemical 

 analysis. The powder separated by the heavy solution varied 

 in specific gravity between the limits 3*165 and 3*235. It 

 showed only a trace of impurities when examined with the 

 microscope, probably of partly altered spinel, which accounts 

 for the small amount of A1 2 0„ shown by the analysis. That 

 the mineral is really chondrodite is proved by the chemical 

 analysis, as will be shown later, while from the same locality 

 there is in the Brush collection a small specimen, Catalogue 

 No. 2057, corresponding exactly in color and showing crystals 

 that could be measured and identified as chondrodite. These 

 are associated with an ash-gray amphibole and have evidently 

 weathered out from limestone. 



The crystals are attached so that only the following forms 

 could be identified : 



c, 001, O 



111, -1 



r„. 125, 



A hemidome, probably 102 or 305 was also 

 present but could not be identified with cer- 

 tainty. The ciwstals are twinned about the 

 base and have the habit shown in figure 1. 

 Only approximate measurements could be 

 made. 





Measured. 



Calculated for 

 chondrodite. 



c ^n„, ooiAiii 



c a* 1 ,, 001^125 

 r 0/N r 2 , 125^125 



= 76° 30' 

 = 54 

 =: 94 



76° 50' 

 54 10 

 94 5l£ 



The analysis will be given later. 



Chondrodite from the Tilly-Foster mine Brewster, Putnam 

 Co., N. Y. — The material for analysis was selected wholly 

 from isolated crystals, which were obtained by the authors at 

 the locality. Each crystal was measured and found to possess 

 characteristic chondrodite forms. The habits of different crys- 

 tals varied considerably but conformed in general to types 

 figured by E. S. Dana. The forms identified by us and some 

 of the measured angles are the following : 



h 



010, 



i-l 



-n» 111, 



, 1 



r lt 127, 



f-2 



c, 



001, 



O 



r„, 125, 



-1-2 



r s , 123, 



f-2 



V 



,012, 



f* 



r], 121, 



-2-2 



nt 2 , 321, 



3-1 



Measured. Calculated. 

 U a n, 125 a 125 = 94° 51' 94° 51£' 

 r s *r u 127 a 127 = 79 15 79 24 

 r 8 '.A*- s j 123 a. 23 =112 431 H2 55 

 Ti a7- s , 127 aI23 = 21 54 21 53 



Measured. Calculated. 

 r s An, 123 a 121 =31° 39£' 31° 39' 

 b > u, 010 a 121 = 26 3 25 58 



r a aw 2 , 123 a ill = 19 42 ' 19 31£ 

 «t,Aii,, 321 a 111 = 13 46 13 42 



