Genth.] 



398 



[Sep. 19, 



of corundum, the other (2) from a piece from the Cullakeuee Mine, Clay 

 County, North Carolina. 



Si0 2 



A1A 



Fe 2 3 



FeO 



MgO 



Li 2 



Na,0 



K 2 6 



Ignition 



17.88 



9.53 



100.69 



100.02 



100.35 



The oxygen ratio of RO : R,0, : SiO, : H,0 = 1 : 1.88 : 1.G4 : 

 0.33, which is nearest to 6 : 12 : 10 : 2, which can be expressed by 

 the formula : 3 (2 RO, SiO.) + 2 (2 R,0 :J > Si0 2 ) + 2 H 2 0. 



About one-fifth of RO are alcalies R.,0. 



25. Pattersonite. 



The chloritic mineral associated with the lesleyite at Unionville and 

 described by J. Lea (L c.) under the name of pattersonite, has been 

 analyzed by S. P. Sharpless (I. c.) who determined, as he says, the pot- 

 ash by difference, and gives 11.35 per cent, of it. But (as Prof. Brush 

 first pointed out) his analysis, exclusive of the potash, sums up only 

 78.64 per cent. A re-examination was therefore very desirable. Dr. J. 

 Lea has very generously furnished for this purpose the material of this 

 rare mineral, of which I have made the following analyses : 



Sp. Gr. = 2.810. 

 Nearly Pure. Purest, 

 29.89 29.90 



27.59 

 3.12 

 9.17 

 17.10 

 trace. 

 0.58 

 2.33 

 11.51 



SiO., 



A1A 



Fe 2 :! 



FeO 



MgO 



Li 2 



Na 2 



K 2 



Ignition 



130. 



87 



9.17 

 17.53 



trace. 



0.83 



2.41 



11.60 



13.80' 



9.43 



102.30 101.30 



The oxygen ratio of RO : R 2 3 : Si0 2 : H.,0 is = 2.05 : 3 : 3.47 

 : 2.22 = 6 : 9 : 10 : 6, corresponding with : 2 (3 RO, SiO,) + 3 

 (RA Si0 2 ) + 6 HA 



The oxygen ratio is very near that of thuringite, which is 1 : 1.5 : 

 1.5 : 1. 



