﻿216 Clarke and Diller — Turquois from New Mexico. 



H 2 



12-88 



Si0 2 



52-38 



Al 2 3 + Fe 2 0, 



33-49 



PA 



none 



MoO 



1-17 



CaO 



trace 



99-92 



Although the mineral itself was white, the alumina from it 

 was distinctly reddish with the iron. 



Under the microscope the rock is seen to be composed 

 chiefly of feldspar, with a considerable amount of biotite, 

 epidote, pyrite and limonite, and some amorphous substance. 

 It is somewhat microgranitic in structure, and the irregular, 

 interlocking grains of feldspar vary in size from -01 to -8 mm 

 in diameter. Most of them are considerably kaolinized, so as 

 to appear cloudy in ordinary light; but between crossed nicols 

 the original outlines of the grains become more distinct. Their 

 optical properties indicate that the feldspar is orthoclase ; an 

 opinion which is fully borne out by the subjoined analysis of 

 the rock, which shows a remarkably large proportion of potash. 



H 2 3-28 



Si0 2 56-68 



A1 2 3 16-62 



Fe 2 3 6-50 



P„0. -73 



•79 



CaO -59 



CuO trace, undet. 



MnO 1-02 



FeS 2 2-21 



K 2 11-18 



Na„0 1-03 



100-63 



The porphyritic crystals are generally Carlsbad twins with 

 irregular outlines. There are occasionally small grains of 

 fresh, transparent plagioclase, which has evidently resulted 

 from alteration. 



The biotite of the rock occurs in noteworthy quantities, but 

 is very unequally distributed. It is frequently aggregated in 

 groups of scales, and may be seen most abundantly in small 

 cavities. It sometimes occurs intimately associated with the 

 turquois, but unlike the latter it is one of the primary min- 

 erals. The small quantity of quartz present is a secondary 

 product, so intimately associated with turquois as to suggest 



