﻿On a New Alkali HornUende. 



83 



Ca (Mg, re)3 Si40i2, and the orthosilicate (E2E)3E2Si30i2, 

 for which he employed the name syntagmatite, originally 

 given by Breithaupt to a black hornblende from Vesuvius. 

 The hornblende from the Island of Jan Meyen, analyzed 

 by Scharizer/ and that from Bohemia, analyzed by 

 Schmidt,^ agree closely with the so-called " syntagmatite 

 molecule." The Stenzelberg mineral, analyzed by Eam- 

 melsberg,^ also approximatee to it ; but these three and 

 the Dungannon hornblende are the only ones yet examined, 

 so far as we are aware, that give at all closely the syntag- 

 matite ratios. The following table gives the analyses of 

 these four minerals and the molecular ratios deducible 

 from them : 



















Dungan 





Jan Mayen. 



Molec. R. 



Bohemia. Mol. R. 



berp:. 



Mol. R. 



non. 



Mol. R. 



SiO. 



Tio; 



39167 



653 653 



39-66 

 0-89 



661 

 11 



672 



39-62 

 0-19 



2(662 



34-184 

 1 -527 



«™j589 



Al.,0, 



14-370 



-0)2.8 



14-83 



145 



222 



14-92 



^^4^}-0 



11-517 



']IV^ 



Fe,03 



12-423 



12-37 



77 



10 28 



12.621 



FeO 



5-856 



8n 





1-97 



271 





7-67 



1061 



21 -979 



3051 





MiiO 



1-505 



21 











0-24 



3 





0-629 



9 





MgO 



10-521 



263 





14-25 



356 





11-32 



283 





1 -353 



34 





CaO 



11-183 



200 



^648 



12-74 



227 



y 663 



12-65 



226 



685 



9-867 



176 



^620 



K.U 



2-013 



21 





1-25 



13 





2-18 



23 





2-286 



24 





Na.O 



2-478 



40 





2-47 



40 





1-12 



18 





3-290 



53 





H.O 



-396 



22 j 





.. J 





0-48 



26 j 





0-348 



19J 





99-912 



100-43 



100-67 



99-601 



In all four analyses the ratios for (E2O + EO) : E2O3 

 (including TiOj when present) are practically 3:1: 

 to give the exact figures (excluding water) : 



(R^O + RO) : R2O3 : SiO^ 



Jan Mayen 2*87 : 1 : 2-99 



Bohemia 2*99 : 1 : 3*02 



Stenzelberg 3-14 ; 1 : 3-15 



Dungannon 3*12 : 1 : 3*07 



:Si02 

 3, or. 



1 loc. cit. 



Min. Mitth., iv, 23, 1881. 



3 Pogg. Ann., 1858, ciii. 454. 



