SALMON — ON ROCKS. 237 
also found to correspond with the leading physical varieties of 
the mineral. 
A 
B 
C 
D 
E 
1 
1 
1 
1 
1 
Sesqui-oxide bases .... 
3 
4 
6 
9 
12 
Silicic and Boracic acid . . 
5 
6 
8 
12 
15 
O.Q. (B) . . . . 
0.8 
0.838 
0.875 
0.833 
0.866 
A. Yellow and brown Tourmaline, with little ¥e (2) and the 
largest quantity of Mg (11) ; together with B (9), FI (2), JTa (2), 
Ca (1), and some K. 
B. Black Tom-maline, containing a mean proportion of ^'e (7) and 
Mg (8) ; together with B (8), Fl (2), l^a (2), Ca (1), and some iL 
C. Blackest, with largest proportion of Iron, S'e (8), Fe (6), and 
least of Mg (2) ; together with 'B (8), Fl (2), Na (1), with some 
Ca and K. 
D. Violet, blue, green, generally containing some Li, ¥e (5), and 
Mn (3) ; together with B' (7), I^a (2), Fl (2), Mg. (1), with some Ca 
ajidK. 
K Red Tourmaline, with Li (I) but no Iron ; together with B (8), 
Fl (2.5), Na (2), K (1), and Mg (1). 
The whole of Rammelsberg's analyses, classed on these five 
divisions, are to be found in Brooke and Miller's edition of " Phillips's 
Mineralogy." Schorl, the black variety, is the most abundant. 
Hennaim divides all the varieties of Toui-maline into three species, 
with the following formulae, the R bases being placed in the order of 
quantity, and the Al being assumed to be replacable by Fe. 
1. Schorl . . (Fe, Mg, Li, Na) B+ Al gi. O.Q. = 1.0 
2. Achfoite . 2 (Na, Li, Mg, Mn) B + 3 Si^. O.Q. = .9090 
3. Rubellite 2 (Na, Li, Mn, Mg) ^B + 3 11^ Sis. o.Q. = 1.0 
assuming the Boracic acid to be a binoxide. 
We find by pseudomorphs that Tourmaline is convertible into Mica, 
Chlorite, and Steatite. In these alterations Al is always separated, 
until in Steatite, the final product of alteration, it disappears. 
Besides this, the decomposition takes place in two diJferent directions : 
in the conversion into Mica, alcaliea are introduced ; while in the 
TOL. H, 
T 
