1890-91.] GOLD AND SILVER IN GALENA AND IRON PYRITES. 121 



THE OCCURRENCE OF GOLD AND SILVER IN GALENA 

 AND IRON PYRITES. 



By R. Dewar. 



(Read 2gth November, iSgo.) 



Galena occurs principally in the Silurian and Carboniferous ages. In 

 America deposits occur in the Lower Silurian, Canadian period, and 

 Calciferous epoch, and in the Trenton period, and Trenton epoch. In 

 the Upper Silurian, the Niagara period, and Medina epoch, Carbonifer- 

 ous age, Subcarboniferous period in Missouri. In Europe in Lower 

 Silurian, in the Lower Llandeillo, in Shropshire, in Caradoc formation, 

 in Montgomery and Cardiganshire, in Stage D of Barrande at Priyi- 

 bram, in Bohemia, in Granada, Jaen, and Sierra DeGador, at the foot of 

 the Sierra Nevadas in Spain.* The deposits at Leadhills, Lanarkshire, 

 Scotland, are also of the Lower Silurian age. Devonian in Devon and 

 Cornwall, in England ; Lower Devonian in the Hartz at Andreasburg, 

 and Clausthal ; Upper Devonian at Vedrin, in Belgium. 



In Carboniferous age, Subcarboniferous period, in mountain limestone 

 in Cumberland, Durham, Northumberland, Yorkshire, Derbyshire and 

 Flintshire, in England ; and in county Wicklow, Ireland. 



The only deposits of any importance which lie outside of the palaeo- 

 zoic time are those of Bleiberg and Baibel in Carinthia, Austria, which 

 are supposed to occur in rocks of the Muschelkalk age. 



Iron pyrites is found in rocks of all ages from the oldest to the most 

 recent formation. 



Galena and iron pyrites are very often found associated with one 

 another. 



Both of these sulphides have in some instances been deposited from 

 solution as is attested to by their being found in indurated clay, and 

 in nodules of chalk in clay ironstone from the coal measures ; pyrites is 

 even found as galena is, quite commonly as sheets or coatings between 

 the layers of bituminous coal and also on anthracite, as well as pseudo- 

 morphs of both animal and vegetable origin. 



Galena is found in granite, sandstone, argillaceous and limestone 

 rocks. Its matrix is generally either quartz, fluor spar, baryta, or calcite, 



*De Verneul thinks this formation is Triassic. 



