Related Physical Properties of Topaz. 



391 



Tenagari, Mino, Japan. — The material was taken from a 

 colorless, transparent crystal, in habit like those from Adun- 

 Chalon. 



Minas Geraes, Brazil. — Transparent, yellow crystals se- 

 lected from a suite of specimens in the Brush collection. 



We take pleasure in expressing to Mr. Geo. L. English of 

 New York our thanks for generously supplying us with the 

 specimens from Nathrop, San Luis Potosi and Japan. 



The following complete analyses have been made : 





I. 



Si0 2 .. 



31-93 



A1,0, . 



56-26 



F .... 



20-33 



HO.. 



•19 



II. 



20-41 



O. equivalent to F. 



Utah. 



Average. 



31-93 

 56-26 

 20-37 

 •19-1-9: 



Ratio. 

 •532 



0-98 

 1-015 



2-02 



Theory for 

 (AlF)»Si0 4 



32-61 

 55-44 

 20-65 



108-75 



8-58 



108-70 



8-70 



10017 



100-00 



Nathrop, Colorado. 



SiO Q 32-23 -537 



A1 2 3 56-01 -550 



F -- 20-42 1-075) 



H 2 -29^9= -032f 11U ' 



108-95 

 O. equivalent to F. 8-60 . 



100-35 



Ratio. 



0-99 

 •1-01 



2-03 









Japan. 









T. 



II. 



Average. 





Ratio. 



SiO„ ... 



32-28 



_ 



32-28 





•538 -98 



Al.O,-- 



56-61 





56-61 





•555 1'02 



F 



HO ... 



19-41 



•57 



19-60 



19-50 

 •57^-9= 



1-C27 ) 



: -063 X 



1-090 2-00 



O. equivalent to F. 



108-96 

 8-21 



100-75 



