38 W. T. JSchaller- — Crystallized Turquoise from Virginia. 



much striated. . The clinopinacoid ~b {010} Is very small and 

 uneven and gives a very poor reflection. The dome h {Oil ^ is 

 the only terminal face definitely determined and is strongly 

 striated on crystal -No. 1, while perfectly smooth and yielding 

 an excellent reflection on crystal No. 2. It may be that the 

 face of k on crystal No. 2 is a cleavage face, as an easy cleavage 

 parallel to this dome was noted by Maskelyne on chalcosiderite. 



The habit of the crystals is shown in figure 1. 



The pointed appearance of the minute crystals is due to the 

 sharpness of the corners where the intersections of Jc {011} with 

 the faces of the prism zone yield acute points. 



Chemical Composition. 



Abundant material was on hand for the analysis, which was 

 made on carefully selected pieces free from all impurities 

 except for the quartz. It was found that the mineral is insol- 

 uble in boiling hydrochloric acid, but after gentle ignition 

 (when it has turned brown) it is readily soluble in acids. The 

 mineral does not lose any water below 200° and retains its 

 blue color at this temperature. Between 200° and 650° all 

 the water is given off* and the mineral becomes greenish in 

 color. On higher heating the greenish color changes to a 

 brown. The mineral is infusible before the blowpipe but 

 becomes brown. 



The average analysis is shown in the table below in the first 

 column, while in the second column is given the same analysis 

 with the insoluble matter (quartz) deducted. The ratios 

 derived herefrom are also given. 



Analysis and ratios of turquoise. 



Analysis 



P 2 5 .._ 29-84 



Al 2 O b 31-91 



Fe 2 3 -18 



CuO 7*87 



H 9 .__ 17-59 



Insol -. 12-57 



Same with 



insol. matter 



deducted 



34-13 





Eatios 





•240 



2-07 or 



2 



36*50 

 •21 



•357 

 •001 



3-09 " 



3 



9-00 



•113 



•97 " 



1 



20-12 



1-118 



9-64 " 



9 



99*96 99-96 



The formula derived from the ratios of the analysis is as 

 follows : 



Cu0.3Al 2 3 .2P 2 6 .9H 2 0. 



* Nearly all of the water is expelled below 400°. 



