Ridden and Hillebrand — Description of Rowlandite. 209 



solution. Three determinations of silica gave 25*98 per cent, 

 2646 per cent and 25 64 per cent. A small amount of lime 

 was also found. The loss on ignition was 2*01 per cent, but 

 this was then considered as wholly due to hydroxyl and that 

 fluorine was present was not even suspected. The apparent 

 shortage, of nearly 5 per cent, was thought to be due to alka- 

 lies, magnesia and other non-essential elements and also to the 

 fact of the hurried character of these preliminary analyses. 

 That the mineral was essentially unlike gadolinite and could 

 not be considered as a non-thoriferous yttrialite seemed proven 

 and so it was laid aside until it could be looked into thoroughly. 



Prof. Rowland photographed the spectrum of this mineral 

 and also the " earths " from its oxalates and found them to be 

 not essentially different from those of gadolinite and other 

 minerals rich in yttria. He, however, expressed the opinion 

 that there were at least a dozen unknown elements in the so- 

 called yttria group not yet separated. The scale on which he 

 showed its spectrum represented a length of ten feet and over 

 ten thousand lines were noticed. 



Later, the density was determined as 4515, on carefully 

 selected fragments. Its color varies from bottle- to pale drab- 

 green when pure and its luster on a fractured surface is de- 

 cidedly more vitreous than that of gadolinite. It is also more 

 transparent, being perfectly so, in thin splinters. Its altera- 

 tion product is of a waxy-brick-red color tending towards 

 brown and this is peculiarly characteristic. The alteration has 

 been one of further oxidation of the iron, hydration and par- 

 tial change to carbonates. 



The mineral is isotropic, its hardness is 6, its fracture glassy- 

 conchoidal, its luster vitreous-resinous and the powdered min- 

 eral is light greenish gray. It is easily soluble in acids with 

 gelatinization. Before the blowpipe it swells up without 

 appreciable glowing but when strongly heated it emits a bril- 

 liant light without fusing. Any change of density was not 

 investigated. The above data warranted me in calling the 

 mineral new and quite distinct from gadolinite with which it 

 is found associated. I proposed therefore, in a note published 

 in this Journal in November, 1891, " the name of Rowlandite 

 after Professor Henry A. Rowland, whose spectrographic 

 work on the so-called ' rare earths ' is so novel and important." 



Through the kindness of Prof. F. W. Clarke, of the U. S. 

 Geol. Survey, it has been possible to complete the description 

 of this new mineral with the analysis and discussion of its 

 composition by Dr. W. F. Hillebrand, given in the following 

 pages. 



Am. Jour. Sol— Third Series, Vol. XLYI, No. 273.— Sept., 1893. 

 15 



