BULLETIN O^ THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 23, pp. 329-332 JULY 15, 1912 



SAPONITE, THALITE, GREEXALITE, GREENSTONE^ 



BY X. II. WIXCirKI.T. 



(Head hij title before the Sorirli/ Decruilter J7. lUll) 



CONTENTS 



Pa {TO 



Sapoiiite ;J20 



Tlmlite 380 



(Jreeiialite . . / ?y\\() 



Serpentine 331 



Conclusions .331 



Sapoxite 



A soft, soapy eartli, varying in coior from nearly white to greenisli 

 and l)liiisli colors, has heen known for more than a hundred and tifiv 

 years. It ha.s heen called sonpstone and porreltanons earth. It was 

 found to fill ca\ ities in rocks, and especially in those rocks that contain 

 little or no ])()lassiuni, such as hasic trap rocks. It is a hydrous silicate 

 of alumina and magnesia, essentially, but with a little iron and some- 

 times a little lime, and its optical elements have not heen ascertained 

 (System of Mineralogy). To this mineral Dana referred several species 

 that were studied later and whose optical characters were determined, at 

 least in part, and which had a similar origin, snch as bowlingite, thalite, 

 and some glauconite. Bowlingite was found to be derived directly from 

 an alteration of olivine, one of the common magnesian minerals of basic 

 igneous rock.- Thalite was found to have an internal vermicular struc- 

 ture and definite crystalline elements,^ while glauconite as a term is 

 divisible into true glauconite, carrying some potassium, and a potash- 

 free variety which fills cavities in igneous rocks, and can easily be affili- 



1 Manuscript received by the Secretary of the Society December 13, 1911. 

 - American Geologist, vol. xxiii, 1899, p. 43. 

 3 American Geologist, vol. xxiii. 1899, p. 41. 



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