190 NOTES ON THE CORUNDUM OF 



ZOISITE. 



This mineral occurs in two forms— a black variety and a 

 light-green variety. These minerals have been called by some 

 Arfverdsonite, but neither of them have the composition of that 

 mineral. Their compositions were as follows : Green variety 

 is of a very pale chrome-green, containing and compared with 

 that from Lake Geneva 



Light green. Lake Geneva. Black variety. 



Silica 45.70 43.59 45.90 



Alumina 24.01 27.72 13.34 



Peroxide of iron 4.56 2.61 11.46 



Lime 13.44 21.00 12.20 



Magnesia 8.03 2.40 12.53 



Soda 2.91 3.08 3.39 



Water 60 .66 



Oxide of chrome 52 



ANDESITE. 



This mineral occurs mostly in a granular form. Its com- 

 position is 



Silica 64.12 



Alumina 24.20 



Soda 9.28 



Lime 2.80 



Oxide of iron , .14 



The other minerals associated with this emery formation 

 are magnetic oxide of iron, chrome iron, rutile, asbestus, talc, 

 actinolite, black tourmaline, chalcedony, anthophyllite, spinel, 

 albite, and picrolite. 



on the existence of the euby and sapphire in north 

 Carolina and Montana Territory. 



The corundum locality that I have described in North 

 Carolina furnishes masses of corundum from which small 

 pieces can be detached, of good blue or of ruby color, perfectly 

 transparent, and nearly free from flaws. When cut and pol- 

 ished they are gems of no mean value. I have not seen the 

 most perfect of them that have been cut, but I have some 

 polished specimens of fine color but with many flaws. 



The question naturally arises, what may be the prospects 

 of obtaining the gem from that locality in sufficient quantity 

 to warrant exploration ? Up to the present time its occurrence 

 is so different from those in known localities in the East Indies 



