142 On the Paragenetic Relations of Minerals. 



which are therefore worked only in virtue of the silver and 

 gold present in the minerals they contain. The Saxon lodes 

 of this formation are especially characterized by a variety of 

 mispickel, in small crystals with a brilliant lustre, generally 

 imbedded in quartz, and very rarely implanted upon it. There 

 is always some gold in this ore, although, in most instances, 

 not sufficient for profitable extraction. It is, indeed, very pos- 

 sible that the presence of argentiferous blende and glance, 

 as well even as that of metallic silver, was determined by 

 this mineral. 



There are good reasons for the opinion that the lodes of 

 this formation are intimately connected, as regards their ori- 

 gin, with metamorphic phenomena in the adjoining rocks, and 

 that they are on a larger scale essentially the same as the 

 small and sometimes metalliferous quartz veins in felsite 

 rock and porphyry. 



Antimony, tellurium, and arsenic, constitute, by reason of 

 their analogy, a mineralogical and chemical group, and their 

 natural compounds frequently appear to belong to one and 

 the same lode formation. Antimony glance always contains 

 traces of gold and silver, in some localities sufficient for ex- 

 traction, and it is very probable that the Transylvanian lodes 

 bearing quartz with auriferous and argentiferous tellurium 

 minerals, and even metallic gold, are of this class. 



The gold occurring in lodes of this formation is very recent, 

 being implanted upon antimony glance, iron pyrites, calcite, 

 realgar, and even gypsum. In like manner, silver appears 

 to be the most recent member of the formation ; consequently 

 it is hardly to be doubted that these metals have originated 

 by some mode of extraction from compound minerals. 



IV. Pyritic lead and zinc formation. — This very closely 

 resembles the last- mentioned formation, from which it is se- 

 parated only on account of the peculiar character communi- 

 cated to it by the considerable masses of galena, black zinc- 

 blende, arsenical iron, sulphur, and magnetic pyrites, and 

 the absence of any considerable quantity of gold or silver in 

 them. Generally speaking, these minerals have been converted 

 into pseudomorphic bisulphurets. The presence of copper py- 

 rites is likewise distinctive ; the edle quartz of Freiberg is, 



