3G0 On the Paragenctic Relations of Minerals. 



tive. They do not bear ore either in the old red sandstone or 

 the schistose rocks, except when covered by the zechstein. 



It may perhaps be assumed that a sudden eruption of 

 substances containing metals, especially copper, took place 

 in the sea from which the cupreous slate and other members 

 of the zechstein were deposited, and undoubtedly from lode 

 fissures. The contorted position of the fish in the cupreous 

 slate is a sufficient evidence of their sudden death. A si- 

 milar opinion was already entertained by Werner ; but the 

 metallic substances with which the sea was impregnated 

 were not precipitated at once, and probably not entirely 

 until the formation of zechstein was completed. In several 

 parts of this series — for instance, at the south-western 

 Rothenberge — to nearly 150 feet above the cupreous slate, 

 nodules, and disseminated masses of copper pyrites, are 

 found, which have been partially converted into malachite 

 and brown iron ochre. If, then, cupreous slate is of sedi- 

 mentary origin, still the copper, silver, and other metals pre- 

 sent in it, have been derived from eruptions through lode 

 fissures. If there were any clue to these lodes, it is probable 

 that they will be found to yield rich supplies of ore. 



The true primitive cobalt and nickel minerals usually occur 

 in lodes called " riicken," because they are almost always con- 

 nected with elevation or depression of the sedimentary rocks, 

 partly in cupreous slate alone or in weissliegenden, or when 

 it and the old red sandstone are wanting, somewhat lower 

 down in the slate rocks ; partly, but generally only for short 

 distances, in the upper zechstein. The vertical height of the 

 lodes is consequently in many cases very limited. Although, 

 in some districts where this formation exists, the occurrence 

 of the minerals above the cupreous slate is unknown, it is 

 certainly the case near Saalfeld. But under all circumstances, 

 where the lodes are continued in the rothliegenden or schis- 

 tose rocks, they are wholly unproductive where the covering 

 of zechstein is wanting. 



Although no true cobalt or nickel minerals are found 

 even in cupreous slate, when it has no " riicken,'' still there 

 is at Saalfeld, sometimes in the delicate fissures parallel to 



