128 Pratt — Mineralogical Motes from Worth Carolina. 



Anorthite. — The occurrence of this feldspar at Buck Creek, 

 Clay Co., N. C, has been mentioned by J. V. Lewis.* The 

 mineral forms with olivine a mass of forellenstein (troctolite) 

 rock, outcropping over an area of about two acres. The par- 

 ticles of feldspar vary in size from that of a pea to some 

 nodules that were an inch and a half long by three-quarters of 

 an inch broad and are separated from the olivine by a zone of 

 fibrous silicates, composed partly of enstatite. 



The feldspar has suffered some kaolinization but the interior 

 of the larger nodules is free from all decomposition. By 

 means of the heavy solution a product was obtained for analysis 

 that varied in specific gravity from 2*6995 to 2*7440. 



The results of the analysis made by C. H. Baskervillef are 

 as follows : 



Ratio. 



SiO 



44-05 

 30-87 



•84 



•754 

 •302 

 •Oil ) 





2-23 



Al _ 



•92 



FeO _. 





CaO 



17-30 



•308 [ 



•328 



1-00 



MgO _ 



•36 



•30 ) 







Na 2 



3-65 



•057 







K 2 



•83 



•009 







Moisture . 



•35 









Loss on ignition 



1-60 











99-85 





The ratio of Si0 2 : A1 2 3 : CaO, is near to 2 : 1 : 1, which iden- 

 tifies the feldspar as an anorthite. 



Mineralogical Department, 

 North Carolina Geological Survey, December, 1897. 



* Bulletin No. 11, N. C. Geological Survey. 



f Of the chemical department of the N. C. Geological Survey. 



