1885.] 



43 



[Genth. 



99.36 



99.15 



The feldspar which is found associated shows large cleavages and is dis- 

 tinctly striated. It gave the composition of oligoclase : 



Silicic oxide = 62.32 



Aluminum oxide = 25.19 



Calcium oxide = 5.01 



Sodium oxide = 8.02 



Potassium oxide = 0.25 



100.79 



12. Topaz from Stoneham, Maine. 



I have made last fall, at the suggestion of Mr. G. F. Kunz, an analysis 

 of the Stoneham topaz, of which he furnished me with a perfectly trans- 

 parent and colorless fragment, in order to clear up the doubt then existing 

 about its composition, on account of an analysis published by Mr. C. M. 

 Bradbury (Chemical News, xlviii, 109), which had given very unusual 

 results. 



Although by the very elaborate investigation of F. "W. Clarke and J. S. 

 Diller (Am. Journ. Sc. [3] xxix), the main question has been settled by 

 showing that the Stoneham topaz has the accepted composition of topaz, 

 I may put on record the results which I have obtained : 



Spec. grav. 

 Si0 2 

 A1 2 3 

 Fl 



Deduct oxygen 



3.553 

 32.03 

 57.18 

 18.83 



108.03 



7.92 



100.11 



13. Orthoclase from French Creek, Chester Co., Pa. 



A peculiar variety of orthoclase has lately been found at the iron mines 

 of the French Creek region, of which Dr. A. E. Foote has presented me 

 with several specimens. The crystals are columnar, very imperfect, but ap- 

 pear to show the planes P, M and n (Naumann) ; they are deeply striated 

 and the slender crystals from 1 to 2 mm in thickness and about 50 mm in 

 length are radiating from a centre, forming sheaf-like or club-like aggre- 



