346 Pei) field — Chemical Composition of Turquois. 



Art. XXXIV. — On the Chemical Composition of Turquois ; 

 by S. L. Penfield. 



•Through the kindness of Mr. Ernest Schernikow of New 

 York City, the writer has recently received a suite of turquois 

 specimens from deposits in Los Cerillos Mts., New Mexico, 

 and the Crescent Mining District, Lincoln Co., Nevada, and 

 one fragment of exceptionally fine quality from the last named 

 locality was presented with the special request that it should 

 be used for chemical analysis. The material was very tine- 

 grained, of a beautiful robin's-egg blue color, and broke with a 

 smooth fracture. A thin section of the material appeared 

 translucent and almost colorless, and when examined under the 

 microscope, the turquois seemed to be perfectly uniform, show- 

 ing no evidence of being made up of two substances, such, for 

 example, as an aluminium phosphate, mixed with a copper salt 

 as coloring material. The material was so fine-grained that no 

 clue as to its crystallization could be made out, other than that 

 it acted somewhat on polarized light. The specific gravity, 

 taken by suspension in the heavy solution, was found to be 2*791. 



In considering the chemical composition of turquois, it 

 should be borne in mind that analyses have been made of only 

 massive, cryptocrystalline fragments, and although they may 

 be selected ever so carefully, no such guarantee of the purity 

 of the material can be given as when, for example, a well 

 crystallized mineral is analyzed. In order to show, however, 

 that turquois is a material of nearly uniform composition, the 

 new analysis is given below in connection with analyses made 

 by other investigators. Analyses have not been included 

 which show a large proportion of foreign constituents other 

 than silica. The analyses are as follows : 





I. 



II. 



III. 



IY. 



V. 



VI. 



VII. 



Lincoln Co., 



Niohabour, 



Karkaralinsk, 



Fresno Co. 



, Los Cerillos, New Mexico. 





Nevada. 



Persia. 



Russia. 



California. 











Penneld. 



Church* 



Nicolajew.-j- 



Moore % 



Three 



analyses by 



Clarke. § 



p A 



34-18 



32-86 



34-42 



33-21 



31-96 



32-86 



- 28-63 



AiA 



, 35-03 



40-19 



[35-79] 



35-98 



39-53 b 



36-88 



37-S8 



Fe 2 0, 



, 1-44 



2'45 a 



3 52 



2-99 







2-40 



4-07 



CuO 



8-51 



5-27 



7-67 



7-80 



6-30 



7-51 



6-56 



H 2 



19-38 



19-34 



18-60 



19 98 



19-80 



19-60 



18-49 



Insol. 



0-93 















1-15 



16 



4-20 



X 



---« 



MnO -36 











CaO -13 



CaO -38 



--- 





99-53 



100-47 



100-00 



99-96 



98-87 



99-79 



99-83 



S P- g 



r. 2-79 



2-75 



2-89 



2-86 





2-80 







a Given as 



2-21 per cent FeO. 





b Includes 



some Fe 2 : 



i. 



* Chemical News, x, p. 290, 1864. 

 % Zeitschr. Kryst., x, p. 247, 1884. 



f Kokscharow's Min. Russland, ix, p. 86, 1884. 

 § This Journal, III, xxxii, p. 212, 1886. 



