﻿Clarke and, Diller — Turquois from J\ T eiv Mexico. 213 



accounted for otherwise. Silliman reports the turquois as 

 containing 3-81 of copper, which corresponds to 4*78 of CuO; 

 but he gives no other quantitative data. 



In attempting to discuss these results it will be well to 

 compare them with two other published analyses of turquois 

 from different localities. First, we have the figures given by 

 Church* for the well-known variety from Persia ; and secondly, 

 the analysis by G\ E. Mooref of turquois, pseudomorphous after 

 apatite, from Taylor's Ranch, Fresno County, California. 





Persia. 



California. 



H o 



19-34 



19-98 



ai 2 o 3 



40-19 



35-98 



Fe o 3 





2-99 



Fe'O 



2-21 





PA 



32-86 



33-21 



CuO 



5-27 



7-80 



MnO 



•36 







100-23 



99-96 



Sp. gr. 



2-75 



2-798, 2-815 



P 2 5 



H 2 



•225 



1-100 



•231 



1-089 



•231 



1-075 



•234 



1-110 



These analyses, leaving temporarily out of account that of 

 the dark-green variety, agree well with each other in their 

 atomic ratios. Dividing the percentages by the proper mole- 

 cular weights, and treating the bases together, the following 

 ratios appear. 



Total base. 



New Mexico, A, -468 



New Mexico, B, *479 



Persia, -492 



California, '470 



In each case the base stands to the acid in a ratio very slightly 

 in excess of two to one; and that excess may fairly be 

 accounted for upon the supposition that it represents a trifling 

 admixture of limonite. The water is present in a proportion 

 a little under that of five molecules to one of phosphoric acid, 

 the variation here being due to the differences in the percen- 

 tages of copper. If we calculate the amount of phosphoric 

 acid necessary to satisfy the alumina, and then reckon the 

 phosphate so obtained as requiring five molecules of water, we 

 shall have left over a quantity of copper, acid, and water cor- 

 responding to a very simple formula; and the turquois will 

 appear as a variable mixture of the two following salts : 



2Al,0,.?.O i .6H 1 0. 



2CuO.P 2 5 .4H 2 0. 



* Chem. Xews, x, 290. Dana's Mineralogy, p. 5S1. 



\ V. von Zepkarovich and G-. E. Moore. Zeitsch. for Kryst. u. Min., s. 240. 



