‘ 
258 Scientific Intelligence. 
two acids is different for different tourmalines. The ratio in question 
was found to be 
in six varieties ==1: 3: 5 spec. grav. mean 3:05 
in eight * betibtirbs: Goce Hy oe of i 3°10 
in six oe poi: f GKe: Bay. th as * 3°20 
Wax. os odie Pe AD. bc Muala 3:08 
i eo beak 19 ja “* ft 4 sd 
The author divides the tourmalines into two classes :~~A. Dark (brown * 
or black) tourmalines ; these contain no lithia, and the first member of 
their formulas is-always a bisilicate (R* Si?.) B. Light (blue, green and . 
red) tourmalines; these contain lithia, and the first member of their | 
formulas is always a trisilicate (RSi); this class includes the trans- ; 
parent varieties. Class A, is further subdivided into 3 groups, for : 
h : 
Formula R?Si?+38Si. These contain the maximum of magnesia but ” 
very little iron. In this group belong the yellow and brown varieties 
from Gouverneur, N. Y., Orford, N. H., Monroe, Ct., Windisckappel 
in Carinthia, Eibenstock in the Harz, and the Zillerthal. 
-) Magnesia-iron tourmalines.--Oxygen ratio, 1:4:6, Sp. Gr. 3:1. 
Formula R? Si?+-4 These contain on an average from 6-9 per cent. 
magnesia, an cent. oxyds of iron. This group embraces 
- 
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Qu. 
rom Saar in Moravia, Krummau in Bohemia and Langbielau in Silesia. 
comprises two groups. 
iy Tron-manganese tourmalines.—Oxygen ratio 1:9:12. Formula 
RSi-+3H Si. Sp. Gr. 3-08, hese are characterized by containing both 
metals. They comprise the green, blue and violet varieties—the green 
brownish-violet from Elba, and the blue from Sarapulsk in the Ural. 
-) Manganese tourmalines.—-Oxygen ratio 1:12:15. Sp.Gr. 3°04 
Formula RSi+4# Si. These are red or nearly colorless varieties free — 
from iron, as those from Elba, Paris in Maine, Schaitansk in the Ur 
and Rozena in Moravia. oe 
n both classes tourmalines are found which are perfectly opake : ‘ 
when cut parallel to the axis and examined in polarized light. a 
The author has further examined the micas and their relations to the 
aay ES 
ee : 
7. We SIE ee yeaa geatee semmarcse- ce weceeenee ee uF ae? Sate LER EAL - 
* The ratio 1:12:15 is i tly d king $:9:12, 
dk aca sae 15 1s incorrectly deduced by Rammelsberg, by antking Bale 
‘. ayes 
