106 THE CONSTITUTION OF THE SILICATES. [bull. 125. 
Barylite Al 4 (Si 2 7 ) 3 Ba 3 
Sphenoclase Al 2 (Si 2 O 7 ) 3 0a 6 
Rowlandite Fe"(Si 2 7 ) 2 Y 2 (YF) 2 
5. The metasilicates. 
Laubanite Al 2 (Si0 3 ) 5 Ca 2 .6H 2 
Talc* Mg 3 (SK) 3 ) 4 H 2 (?) 
Pyrophyllite Al(Si0 3 ) 2 H 
Kyanite A10(Si0 3 )(A10) 
Beryl Al 2 Gl 3 (Si0 3 ) 6 
Leucophanite 0a(SiO 3 ) 2 Na(GlF) 
Meliphanite Ca 2 (SK) 3 ) 2 (Si0 4 )GlNa(GlF) 
Wollastonite 0a 3 (SiO 3 ) 3 
Pectolite Ca 2 (Si0 3 ) 3 NaH 
Danburite Ca(Si0 3 ) 2 (BO) 2 
Chrysocolla CuSi0 3 .2H 2 0(?) 
Neptunite Ti(Si0 3 ) 4 R"R' 2 
Leucite, pollucite, analcite, eudialyte, etc., have been treated as 
pseudometasilicates. To these species must be added the pyroxenes 
and the ainphiboles, with the following general formulae: 
Pyroxene R" 8 (Si0 4 ) 2 (Si 3 8 ) 2 
Amphibole R" 4 (Si0 4 )(Si 3 8 ) 
Glaucophane and crocidolite may be written 
R // 2 (Si 3 8 ) 2 (R /// 0) 2 ]SIa 2 
or all trisilicate, and crossite, waldheimite, etc., seem to be similar. 
The evidence for these expressions appears in the text. 
6. The dimetasilicates. 
Petalite Al(Si 2 5 ) 2 Li 
Milarite Al 2 (Si 2 5 ) 6 HKCa 2 
Mordenite ) rAl 2 (Si 2 O 5 ) 5 0aH 2 .6H 2 O-i 
Ptilolite 5 LAl 2 (Si 2 5 ) 5 R / 2H 2 .6H 2 J 
Hyalotekite R" 2 (Si0 5 ) 3 (RF)(RB0 2 ) 
* Possibly a p3eudometasilicate. 
