On the Paragenetic Relations of Minerals. 357 



like the aphrite produced from gypsum, to streams of car- 

 bonic acid. 



In no other formation are repetitions of the same consti- 

 tuents so numerous as in this ; three or four are frequent, 

 and in the Reich er Seegen mine at Sachsenburg, pearl-spar, 

 barytite, and tautoklin, are repeated at one place twenty -two 

 times, without a vestige of ore. 



The minerals occurring in the fluo-barytic lodes will be 

 considered under the head of the following formations, with 

 the exception of the iron pyrites, because here this mineral, 

 whether alone or associated with others, always presents a 

 characteristic chemical feature — it is arseniferous. It is highly 

 probable that iron pyrites very generally contains arsenic, 

 although in too small a proportion to be easily recognised. 

 Fritzsche likewise found in the pyrites of this formation, co- 

 balt and nickel to the amount of 1 per cent. On the contrary, 

 pyrites occurring imbedded or disseminated in slate and 

 other rocks, gave no indications of arsenic. Even iron pyrites 

 locally implanted upon arsenical pyrites in old formations 

 gave no sign of arsenic. 



The question of the origin of the barytite contained in the 

 lodes naturally suggests itself. When it is remembered that 

 this mineral is almost always accompanied by sulphurets 

 and arseniurets, which can only have been derived from the 

 interior of the earth, we perhaps cannot do otherwise than 

 assume that its source was the same. But in what state \ 

 Certainly not as a melted mass, scarcely as an aqueous solu- 

 tion. Professor Breithaupt is disposed to consider that it 

 was introduced into the lodes as sulphuret of barium, and 

 subsequently oxidised, and believes the probability that the 

 interior of the earth consists chiefly of metallic sulphurets 

 to be a sufficient ground for this opinion. 



XIII. Later Cobalt and Nickel Formation, Group A. — 

 The constituents of this formation at Schladming (Styria), and 

 Oberwallis (Switzerland), are — 1. The variety of rothnickelkies, 

 whose specific gravity is 7*3, always containing a small per- 

 centage of sulphur, and probably constituting a distinct spe- 

 cies. 2. That variety of nickel-glance called gersdorfite or 

 stirian. True spiescobalt, metallic arsenic, and even arse- 



