144 On the Paragenctic Relations of Minerals. 



served, thus upon galena and blende — mispickel, and then 

 again galena and mispickel. Derivatives of galena are rare, 

 those of copper pyrites unknown. 



This is perhaps the most important formation for the min- 

 ing of Freiberg, for only a small part of the silver which is 

 obtained there is derived from the true silver formation, the 

 principal part being extracted from the galena of this forma- 

 tion. 



It is in connection with this formation that we first meet 

 with a phenomenon called by the miner, the iron hat, gossan. 

 It has been universally found that iron ores, especially brown 

 iron ore, red hematite, and even specular iron ore, are met 

 with only at the upper part and outcrop of the lodes, which, 

 when worked deeper, yield ores of more valuable metals. 

 There is indeed historical evidence that the working of iron 

 ores has laid bare ores of silver, lead, copper, cobalt, and 

 nickel, and in many districts the proverb is still in use — 



" Der Gang hat einen eisernen Hut, 

 Undthut darum in der Teufe gut." 



It is scarcely probable that this phenomenon can in all 

 cases be accounted for in a similar manner. It is met 

 with in lodes of the pyritic lead and zinc formation in some 

 of the Freiberg mines, and there it may have originated 

 from the action of the atmosphere upon pyritic minerals. 

 There are brown iron ores which are remarkable for contain- 

 ing silver sometimes in available quantity, called in Germany 

 " edle Braunen" and " Gilben," in Mexico " Pacos." It is 

 possible that in the earlier periods of mining in Germany, the 

 belief in the " eisernen Hut " was more universal than at the 

 present time ; but in Mexico and South America it still main- 

 tains its ancient authority, and has recently received a con- 

 firmation in the discovery of the lead and silver mines at 

 Jarosa, near Alicante in Spain. Eut the presence of silver 

 in the iron hat is not essential. Probably the knowledge of 

 its occurrence has contributed to the confirmation of the 

 opinion that the deeper a lode is driven the greater is the 

 probability of finding rich deposits of ore, although in this 

 instance there is another genetic reason for the belief than 

 that previously spoken of. 



