358 On the Paragenetic Relations of Minerals. 



nical pyrites, are said to occur at Schladrning. If the latter 

 mineral is really present, it may perhaps indicate that the 

 lode is of very remote date. Calcite is a recent member. 



Judging from the little known of a cobalt and nickel for- 

 mation in the Pyrenees, it is not improbable that it should 

 be included under this group. 



Group B occurs principally in the Saxon Voigtland, the 

 Harz, Nassau, Hungary, and Missouri. It is principally 

 imbedded in spathic iron, and can scarcely be regarded as 

 other than sporadic. Nickel is more abundant than cobalt. 



The lodes of this group present in a marked manner the 

 peculiar characters of these deposits ; their saalbands inter- 

 sect the rock, especially when it has a schistose structure. 

 The principal minerals are linneite and the less dense varie- 

 ties of nickel-glance, amoibite, and gray nickelkies. Although 

 galena is sometimes found, the other members of the pyritic 

 formation — zinc-blende and arsenical pyrites — are entirely 

 absent. 



With regard to the succession of pyritic arseniurets and 

 sulphurets in general, the same uniformity obtains, which is 

 more prominent in the third group of this formation. 



1. The mono-arseniurets have been formed prior to the 

 binarseniurets, and it has already been pointed out that this 

 is the case with sulphurets. 



2. The arseniurets have been formed before the sulphurets. 

 Group C. — Perhaps the purest cobalt minerals occur at 



Schneeberg and Allemont ; at other places nickel minerals 

 preponderate; and probably there is in general a greater 

 quantity of nickel than of cobalt. The association of mine- 

 rals containing gold and silver may serve to characterize this 

 group. 



Spathic iron seldom occurs as the bedding ; and when it 

 does there is an approximation to the previous group. Bary- 

 tite is particularly characteristic, although sometimes its 

 existence is only indicated by pseudomorphs, it having been 

 removed during, or rather after, the subsequent formation of 

 quartz. This quartz contains traces of cobalt. It may in 

 general be assumed that the more abundant the later quartz 

 above heavy spar, the more the latter has been removed. 



