MINEKALOGY ; WITH A CLASSIFICATION OF SILICATES. 



47 



the question arises what kind of chemical A^ariation shoiUd take precedence. Considering 

 the general persistence of type in series of protopersilicates like those of the zeolites and 

 the feldspars, in each of which the ratio of protoxyds to alumina is constant, that of the 

 silica being variable, I have, in a tabular view of the suborder, arranged species so related 

 on the same horizontal lines ; while species belonging to the same tribe, but having differ- 

 ent relations between the protoxyds and the alumina, are arranged in successive horizontal 

 lines, those with the larger proportion of protoxyds being above, and those with the 

 smaller proportion below ; so as to represent the passage towards protosilicates in the one 

 direction, and to persilicates on the other. It should here be remarked that in many cases, 

 as in tourmalines and in micas, the species thus vertically arranged present physical resem- 

 blances not less close than those between species on the same horizontal line, as may be 

 seen in the synoptical table of the protopersilicates mentioned below. As regards the 

 relative condensation, the successive species or genera of a tribe on a given line may be 

 placed with regard to the value of V; the denser, or those with the lesser atomic volume, 

 following those which are less dense. 



§ 56. The suborders and tribes of the order Silicate, as already set forth, including the 

 possible Hydroperstpallioids and Perspathoids, are presented in the following table, which is 

 succeeded by a list of the principal species in each tribe. The several minerals of the 

 various tribes in their sequence will then be briefly noticed, and tables of them will be 

 given, showing the atomic formulas of the species, and the values of P and V as calcu- 

 lated therefrom. Finally, the minerals of each suborder, arranged under their respective 

 tribes in the sequence already explained, will be presented in synoptical tables, giving at 



a single view the në\v classification of the silicates.' 



Order SILICATE. 



ÏRIDB 1. Pectolitoid. Calamine,Tliorito, Ce.rito, Gyrolite, Friedelite, Pyrosmalite, Xoiialtite, Plombierite, Hydro- 

 rhodonite, Dioptase, Pectolite, Datolite, Apopliyllite, Okenite; together with ViJlarsite, Matricite, 

 Picrosmine, Picrolite and Cliryssotile- (Table II.) 



TsiiiE 2. Protospathoid. Banalité, Willemitc, Batrachite, Tephroite, Knchelite, Gadolinite, Ilelvite, Leucophan- 

 ite, AVoUa-stonite, Tschefi'ldnite. (Tuljle III.) 



Triije 3. Protad.uiaxtoid. Chondrodite, Monticellite, Clirysolite, Phenacite, Bertrandite, Amphibole, Rhodonite, 

 Pyroxene, Enstatite, Guarinite, Titanite, Danburite. (Table IV.) 



' As regards the designation of the tribes, the use of a term which ends in a syllable expressing likeness to 

 include not only bodies resembling a given type, but the type itself, is justified by the meaning given to .such 

 words as haloid, albuminoid and colloid, and also by the use in liotany of the name of Anidcr for an order which 

 comprises not only Ariicea; but the typical genu.s Arum. 



