On the Paragenetic Relations of Minerals. 361 



the planes of stratification, a coating of erythrine, together 

 with malachite and chessylite ; moreover, cobalt has been 

 detected by analysis as one among the numerous ingredients 

 of this slate. Vanadium has likewise been met with recently 

 in the Mansfeld slags ; it has probably originated from some 

 cupreous mineral, in which it existed as a substitute of anti- 

 mony or arsenic. 



Friesleben expressly states that cobalt and nickel minerals 

 occur less in cupreous slate itself than in the riicken, — i.e. 

 in the lodes traversing it, or when actually in the slate, in the 

 immediate proximity of these riicken. 



All these circumstances render it probable that the con- 

 tents of the lodes called " riicken" have been formed by la- 

 teral secretion, the more so as they do not extend downward 

 to any depth. A direct ascension is thus out of the question 

 here. Quartz would, in such a case, have been brought up 

 from the granite and greywacke slate, but there is no trace 

 of quartz or of silicates. It is not improbable that the car- 

 bonaceous matter of the cupreous slate has chiefly contri- 

 buted, by reduction, to the formation of the pyritic minerals, 

 containing also cobalt, nickel, and arsenic. 



Asbolan, or black erdcobalt, is one of the minerals which 

 contains cobalt with traces of nickel. This occurs in the 

 lodes above the cupreous slate ; in zechstein, which is espe- 

 cially rich in hydrated oxide of iron; indeed, the lodes which 

 bear it do not even extend into the cupreous slate, and ap- 

 pear to be fissures formed by drying, with which zechstein 

 abounds. It has been found by experience that the asbolan 

 near Saalfeld decreases as the cupreous slate is approached. 

 The stalactitic form, and the considerable percentage of 

 water in asbolan, may perhaps be evidence in favour of its 

 being an infiltration product. The large quantity of manga- 

 nese in asbolan may be accounted for by the fact, that the 

 spathic iron, from which the hydrated oxide of iron has prin- 

 cipally originated, contains manganese. 



As might be expected, the group in question of the cobalt 

 nickel formation, is not deficient in the associates of cupreous 

 minerals. In the Mansfeld district they are not very abun- 

 dant on the riicken in cupreous slate and wiesliegenden, still 



