104 THE CONSTITUTION OF TEE SILICATES. [bull. 125. 
With many members of the chlorite group, such as prochlorite, 
leuchtenbergite, etc. 
F. Borosillcates, etc. 
Tourmaline, A Al 8 (Si0 4 ) 6 (B0 3 )(B0 2 ) 2 R' 5 
Tourmaline, B Al 7 (Si0 4 ) 6 (B0 3 )(B0 2 ) 2 Mg 2 K' 4 
Tourmaline, C Al 6 (Si0 4 ) 6 (B0 3 )(B0 2 ) 2 Mg 3 R' 5 
Tourmaline, D Al 5 (Si0 4 ) 6 (B0 3 )(B0 2 ) 2 Mg 4 R' 6 
Axinite Al(SiO 4 )(Si 3 O 8 )(BO 3 )0a 3 (AlOH) 
And the species cappelinite, karyocerite, melanocerite, and tritomite. 
G. Complex silicates. 
Spodumene Al 6 (Si 3 8 ) 3 (Si0 4 ) 3 Li 6 
Jadeite Al 6 (Si 3 8 ) 3 (Si0 4 ) 3 Na 6 
Acmite Fe 6 (Si 3 8 ) 3 (Si0 4 ) 3 Na 6 
And in babingtonite the molecule Fe /// 6 (Si 3 8 ) 3 (Si0 4 ) 3 Fe" 3 
To this group of triad silicates, the largest and most important group 
of all, other species belong which I have not clearly interpreted. Such 
species are halloysite, allophane, collyrite, schrotterite, sapphirin, 
ardennite, carpholite, cenosite, sarcolite, etc. The formulae of the tab- 
ulated species must all be construed in a general way — that is, with 
common replacements of aluminum by ferric iron, magnesium by ferrous 
iron, and so on. In every case details are suppressed, and these are to 
be found in the text. The same rule applies to the species in the groups 
which follow : 
2. Ortho- and trisilicates of dyad bases. 
Forsterite nJ^SiO, 
Fayalite n.Fe 2 Si0 4 
Tephroite n.Mn 2 Si0 4 
Willemite n.Zn 2 Si0 4 
Phenakite n.Gl 2 Si0 4 
Monti cellite 0aMgSiO 4 
Knebelite MnFeSi0 4 
Hyalosiderite Mg 4 Fe 2 (Si0 4 ) 3 
Igelstromite Fe 4 Mn 2 (Si0 4 ) 3 
Trimerite Gl 3 Mn 2 Ca(Si0 4 ) 3 
Ohondrodite Mg 3 (Si0 4 ) 2 (MgF) 2 
Humite Mg 5 (Si0 4 ) 3 (MgF) 2 
Olinohumite * Mg 7 (Si0 4 ) 4 (MgF) 2 
Helvite ) 
Danalite } Gl 3 R- 2 (SiG 4 ) 3 (R-S-R) 
Bertrandite Gl 3 (Si0 4 ) 2 H(G10H) 
Calamine Zn 2 (Si0 4 ) 2 H 2 (ZnOH) 2 
Lievnte '. Fe 2 0a(SiO 4 ) 2 (AlOH) 
Datolite Ca 2 (Si0 4 ) 2 H 2 (BO) 2 
Homilite Ca 2 Fe(Si0 4 ) 2 (BO) 2 
