24 Johnson and Warren — Geology of Rhode Island. 





Ilinen- 



Magne- 



Ortho- 





Anor- 



Oli- 



Per cent 



Mol. 



ite 



tite 



clase 



Albite 



thite 



vine Spinel 



SiO„ 22-35 



•372 







•006 



•042 



•040 



•284 



A1 3 3 .... 5-26 



•051 







■001 



•007 



•020 



•023 



Fe 9 O s ---. 14-05 



•088 





•088 











V 2 3 .... -18 



•001 





•001 











Cr o 3 .... tr. 

















FeO 28-84 



•400 



•125 



•089 









1-86 



MeO 16-10 



•402 













•377 -025 



CaO* .... 1-17 



•020 











•020 





Na„0 -44 



•007 









•007 







K 2 -10 



•001 







■001 









H o O- ... -42 

















C0 o -02 

















TiO„ 10-11 



•125 



•125 













P 2 5 -02 

















S -38 



•012 















MnO -43 



•005 













•005 



Zn* -71 



•010 















Cu -08 



•001 















(Co&Ni) . -08 



•001 















Pb tr. 

















Total.. 10074 



In the non-magnetic residue obtained in isolating the olivine 

 previously described, some sphalerite and chalcopyriteaswellas 

 a few galena and pyrite grains were identified. The sulphur is 

 therefore not all present in the sphalerite and chalcopyrite. 

 Some of the zinc may also enter into the spinel molecule. The 

 amount of sulphides found may be in excess of the amount 

 really in the normal rock. Since the analysis was completed 

 a minute vein of sulphides has been observed in a specimen 

 similar to those used for analysis, but no trace of sulphide has 

 been noted in the rock outside of this vein. It is possible that 

 such a vein slipped unnoticed in to the sample analyzed. In 

 such case, however, the classification is not materially affected 

 thereby. The classification is as follows : 



Or 0-56 sal 9-79 _ . 



Ab 3-67 9-79 sal. f^=^' = °* 10 = 5 > p erfemane. 



An 5-56 P + 45 . 70 . 



Ol 45-70 =- — - =1-1 =3, Rhodare. 



Mt 20-65 90-05 fern. !*■ X/ 2 9 "^ „ QA _ ,. 



Ilm.... .19-00 (MgFe)O + CaO^807 7 = Rhodase> 



Spinel .. 3-55 K„0 + Na 2 8 "1 



Sulphides 1-15 MgO 402 



FeO 405 



99-84f 



^Sphalerite 0-004 Chalcopyrite 0"004 



•j- After the completion of the calculation it was noticed that the dropping 

 off of fractional parts in several instances had resulted in reducing the total 

 of the norm and making a small discrepancy between it and the total of the 



