SALMON — ON THE FORMATION OF ORE-VEINS, 



365 



At Hntte, two leagues from Freiberg, on the edge of the Tha- 

 rander porphyry-mass, and in an isolated stock-form mass, galena, 

 blende, and pyrites likewise occur in drusy vesicles of the porphyry, 

 and gold is even said (although not on entirely reliable authority) to 

 be foimd in the pyrites. But what are particularly and indisputably 

 important for our considerations are the ore-holding felsite-rock or 

 porphyries in the neighbourhood of Braunsdorf, near Freiberg, 

 which H. Miiller ha,s investigated and especially described in this 

 volume. 



Now is it not, at all events, a very remarkable circumstance that 

 in the eruptive porphyry-formations of the environs of Freiberg the 

 same ores and minerals occur disseminated which entirely prevail in 

 the ore-veins of the same neighbourhood ? Certainly, these ore- 

 veins are in general of more recent origin than the porphyries, 

 which they almost everywhere penetrate. But H. Miiller has shown 

 that, at the Reinsberger Grliick Mgg. of Emanuel Erbstolln, the oldest 

 Freiberger ore-veins, those of the great quartz-formation, are also 

 penetrated and disturbed by certain porphyries, and that consequently 

 both formations — ore-veins and porphyries — ^belong to one epoch, 

 in the sense that the fiUing-up of the ore -veins in general is to be 

 considered as a consequence of the porphyry-eruptions. 



A new set of statements or a novel experience can never be sup- 

 ported by too many facts. I shall therefore here again cite that the 

 dolomitic limestone, which at Tharander lies in the oldest clay-slate, 

 sometimes contains, exactly at the point where it is disturbed by the 

 porphyry, crystals of pyrites, copper-pyrites, galena, blende, and 

 baryte, in drusy vesicles. May we not suppose that the occurrence 

 of these minerals here is conditional upon the contiguity of the por- 

 phyry, as in the Freiberger ore-veins ? 



As volcanic activity on the land or at the bottom of the sea really 

 by no means consists merely in the pressing-up of lava, but is most 

 intimately connected with great earthquakes — the opening of 

 fissures, the exhalations of gas and vapours, and the production of 

 hot and mineral springs — so it is also certain that the pressing-up of 

 the older massive rocks was combined with like complicated events. 

 And if, in those earlier periods of geological time, we are entitled to 

 assume the existence of a thick heavy atmosphere, and, as a con- 



VOL. 11. 0 G 



