NOTES ON ALLOPHANITE, FUCHSITE, AND TRIPHYLITE. 



By Edgar T. Wherry, 



Assistant Curator, Division of Mineralogy and Petrology, United States National Museum. 



. OBSERVATIONS ON ALLOPHANITE. 



Nomenclature of the hydrous aluminium silicates. — There are among 

 minerals a nimiber of groups consisting of solid solutions of two or 

 more theoretical end-compounds, in which, for convenience, certain 

 intermediate members are assigned names. To cite one of these, the 

 intermediate members of the plagioclase feldspar group are called 

 ohgoclase, andesine, labradorite, etc., although it would be equally 

 possible to name them all by the proportions of the end-compounds, 

 albite and anorthite, they contain. 



While the hydrous aluminium silicates could also be named 

 according to the proportions of the end-members present, it is perhaps 

 better to assign names to the more important intermediate ones. 

 Dana selected six of these: (1) halloysite, (2) cimoHte, (3) mont- 

 moriUonite, (4) allophane, (5) collyrite, and (6) schrotterite, as 

 species, but of these 2 and 3 differ only in unessential particulars, 

 as do also 4, 5, and 6, so only three are recognized here, the names 

 assigned being those which have priority: 



Cimolite (Klaproth, 1795). — Mostly soft, earthy clays with the 

 ratio AI2O3 : SiOg = from 1 : 7.5 to 1 : 2.5 ; includes anauxite, confolensite, 

 delanovite, erinite (Thomson), hunterite, montmoriUonite, razum- 

 ovskite, some smectite, steargillite, stolpenite, and termierite. 



Halloysite (Berthier, 1826). — Mostly soft, earthy clays with the 

 ratio Al203:Si02 = from 1:2.5 to 1:1.5; includes ancudite, some 

 allophane, bole, catlinite, dillnite, galapectite, glagerite, glossecoUite, 

 gummite (Breithaupt) , indianaite, some kaolinite, keffekihte, lenzi- 

 nite, lithomai^e, meerschaluminite, milanite, nerchinskite, ochran, 

 oropian, pholerite, pseudosteatite, samoite, severite, smectite, tera- 

 tohte, and tuesite. 



Allophanite (Stromeyer, 1816). — ^Harder, more vitreous mmerals, 

 with the ratio Al203:Si02 = from 1:1.5 to 1:0.25; includes carolathite, 

 coUyrite, and schrotterite. Only allophanite will be discussed here. 



Name. — The name " allophan," from two Greek words meaning " to 

 appear different," was given by Stromeyer^ to a waxy, amorphous 



1 Gel. Anz. Kong. Ges. Wiss., Gottingen, 1816, p. 1250. 



Proceedings U. S. National Museum, Vol.49— No. 2118. 



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