Origin of Masses of Tin Ore. 157 
almost an identity between the two classes of formations in 
tin mines. This identity becomes almost absolute when we 
examine the nature of the minerals which usually accompany 
tin, whether in masses or in veins. It is the study of these 
which forms the truly novel part of M. Daubrée’s work, and 
it has led him to ascribe a common origin to them. 
He has found that in all the formations quartz exists in 
great abundance, and that its existence is so connected with 
the presence of oxide of tin, that when the enclosing rocks are 
impregnated with that mineral, they become in general more 
quartzose, as is seen at Geyer and Altenberg. 
After the quartz, which always predominates, whether in the 
large or small veins, and also in the enclosing rock, the most 
constant accompaniments are the fluoric compounds, princi- 
pally fluo-silicates, sometimes fluo-phosphates or fluorides. 
Thus the micas which accompany tin are in general rich in 
fluorine. That of Altenberg contains 3.47 per cent. This 
substance enters in the proportion of from 4.84 to 8.00 in the 
two varieties of Zinwald mica analysed by Gmelin. 
Topaz and schorlite, which contain even a greater quantity 
of fluorine than these micas, are very frequently found in the 
stockwerks of tin; and the latter substance forms a great mass 
in the formation of Altenberg. Lastly, we pretty frequently 
find apatite or the fluo-phosphate of lime, and even the fluo- 
ride of calcium. 
The granitic veins of Finbo, near Fahlun, which contain 
oxide of tin, with tantalic oxide, likewise produces topaz, 
fluor spar, and various fluorides of cerium and yttria. 
In the celebrated topaz and emerald mines of Adon-Tschelon, 
on the Chinese frontier of Siberia, we sometimes find oxide of 
tin, along with wolfram and mica, analogous to that of Zin- 
wald. Lastly, it may be observed that the specimens of tin 
from Greenland, which are to be found in most mineralogical 
collections, come from the same locality as the cryolite, so 
rich in fluorine. 
Thus, according to M. Daubrée, all the stanniferous masses 
known are characterized by the presence of fluorine, the propor- 
tion of which is often considerable, if we compare it, not with 
the total volume of the mass, but with its richness in tin. The 
