148 On the Paragenetic Relations of Minerals. 



base, sandstone, or limestone. Such kind of negative facts 

 must not be disregarded ; this one, for instance, indicates 

 that these lodes are of very remote date, apparently that of 

 the protrusion of the older granite. 



The existence of alluvial deposits of tin ore must not be 

 overlooked. These are, in fact, to be regarded as the result of 

 gigantic natural ore washings. The absence of wolframites is 

 probably owing to the more easy mechanical and chemical 

 destruction of these minerals as compared with the tin ore. 

 Even in lodes, instances of the chemical destruction of wol- 

 framites, and production of scheelspar, have been observed, 

 unaccompanied by any pseudomorphs after tin ore. 



A remarkable feature is presented by the lodes of this for- 

 mation where they come in contact with those of red haema- 

 tites. It has been observed at Altenberg (Saxony), that at 

 the points of contact both lodes are poorer, and frequently 

 the tin ore is altogether absent. 



The lodes of this formation generally possess in a very 

 marked manner the banded structure, especially in the mica 

 slate at Ehrenfriedersdorf (Saxony). 



VII. Clinoedritic lead and zinc formation. — Under the 

 term clinoedrites, Breithaupt understands a mineralogical 

 genus comprising the various kinds of fahlerz, tennantite, 

 copper-blende, &c. 



These minerals are distinguished chemically by their very 

 complicated, although characteristic composition, containing, 

 on the one hand, copper, mercury, silver, zinc, iron, cobalt, 

 and nickel ; on the other hand, antimony, arsenic, and tin. 

 All these metals exist as sulphurets ; those of copper and 

 mercury with two equivalents to one of sulphur; those of 

 silver, zinc, iron, tin, and probably cobalt and nickel, with 

 equal equivalents ; those of antimony and arsenic with two 

 equivalents of metal to three of sulphur. 



The clinoedrites occur in very definite paragenetic rela- 

 tions ; bournonite is frequently associated with them. In 

 many places this formation occurs alone, sometimes together 

 with the older pyritic, or with the more recent fluo-barytic. 



When felspar or iron spar occur in the pyritic lead and 



