Washington — Kaersutitefrom Linosa and Greenland. 201 



the garner group as suggested by Barnmelsberg* and discussed 

 in detail by Koenig.+ in which enough of the apparent Ti0 2 

 is calculated as TL0 3 to conform to the garnet formula, The 

 case of the hornblendes offers more difficulties, since their 

 molecular constitution is not well understood at present, and 

 is undoubtedly very complex, as is well known. 



In a recent important paper, PentleldJ. and Stanley explain 

 the presence of the sesquioxides by " their introduction into 

 the metasilicate molecule in the form of various basic, bivalent 

 radicals." the mass effect of the very complex amphibole acid 

 exerting a controlling influence on the crystal form and other 

 physical characters. They also suggest the possibility that 

 the molecule of the amphibole acid has a ring form, analogous 

 to that of the benzene compounds. By assuming various 

 bivalent j-adicals. composed of K 2 3 with F, HO, Na, and ~R ff , 

 which combine with SiO a in the ratio of 1 : 1, a final residue 

 : : Mg, Fc O and CaO is left which conforms to the same 

 metasilicate ratio. As regards tremolite and actinolite their 

 exact ratios show that the molecule ^a^A^S^O^, suggested by 

 Tseherinak. cannot be present, as this would " deplete the 

 total silica and destroy the 1 : 1 ratio." In their calculations 

 of their analyses of the aluminous hornblendes this molecule 

 was also neglected, and very exact metasilicate ratios were 

 obtained without the assumption of its presence. As this 

 paper is the latest and one of the most suggestive and illumi- 

 nating contributions to our knowledge of the constitution of the 

 amphiboles. a study of our two minerals in its light will be of 

 interest. 



The two analyses made by me yield the following ratios, 

 MnO and XiO being reckoned in with FeO : 



Linosa. 



SiO,_ 



TiO. 



Al 9 O a 



Fe a O s 



FeO_ 



MgO 



CaO . 



Na,0 



K a O 



H a O. 



f: __ 



681 ) 

 106 \ 

 097 j 



: 

 058 / 

 312 \ 

 217 

 032 j 



m \ 



010 ) 



■:-: 



•153 



370 ) 



•217 

 •039 



y '643 



I 

 I 



- '017 j 



Kaersnt. 



•659 [ 



•129 \ 



•110 | 



•008 f 



•123 



•333 



•195 



•048 



•011 



•033 



'4:56} 



•195 

 •059 | 

 •033 J 



•788 



•118 



y '743 



* C. Eammelsberg. Min. Chem.. 1875. 



- 3 A. Koenig, Proc. Acad. Sci.. Phila., 1886, p. 354. 



: rhis Journal, vol. xxiii. p. 23, 1907. 



Foub Set— Fourth Series. Vol. XXVI, So. 153.— September. 1908. 

 15 



