CLAEEE.] 
TOURMALINE GROUP. 
59 
we have the following comparison with Riggs's analysis of Pierrepont 
tourmaline: 
Found. Calculated. 
SiO. 
35. 61 ) 35. 91 
.55 \\ 
10. 15 I 10. 48 
■ -27 J 
25. 29 ) 25. 44 
TiO. 
B 2 , 
F 
ALO, 
Fe,0, 
FeO 
.44 
8.19 
11.07 
3.31 
8.62 
11.17 
9.79 
MffO 
CaO 
Na.O 
1.51 h 1-55 
.20 $ 
3. 34 t 4. 04 
KoO 
H,0 
99. 93 | 100. 00 
Tourmalines which do not correspond to any one of the four types 
given agree with mixtures of them, and all of the analyses of this 
mineral published by Jannasch and Oalb or by Riggs can be reduced 
to suitable formulae. These formulae suggest an end product, 
Al 9 (Si0 4 ) 6 (B0 2 ) 2 B0 3 NaH 
which may possibly exist, but is not known. They also indicate the 
obvious relationship of tourmaline to the micas, and express the ready 
alterability of the former into the latter. A molecule of tourmaline, 
with elimination of boric acid and one atom of aluminum, splits into 
two molecules of the mica type, and the transformation is easily 
understood. Potash is of course taken up. Certain experiments by 
Lemberg,* who investigated the action of alkaline solutions upon tour- 
maline, are in accord with these suppositions. 
Although otherwise interpreted by Brogger, the minerals cappelinite, 
melanocerite, karyocerite, and tritomite seem to be structurally akin to 
tourmaline. This view of their nature has already been suggested by 
Wiik,f and it is sustained both by chemical and by morphological 
considerations. Cappelinite is hexagonal, and the other species, 
like tourmaline, are rhombohedral. They are silicates of rare earths, 
which are mostly trivalent, like aluminum; all contain boron, and all 
but cappelinite contain fluorine also. Furthermore, all four species, 
considered together, illustrate the reciprocity between boric acid and 
fluorine, which has been suggested in the discussion of tourmaline. 
*Zeitsch. Deutsch. Geol. Gesell., 1892, p. 239. 
t Zeitsch. Kryst. Min., XXIII, pp. 421, 422, 1894. 
