Mineralogy of South America. 139 



At the points of contact with the diorite rocks we find fre- 

 quent development of the following minerals, evidently formed 

 by a recombining and recrystallizing action on the components 

 of the strata themselves, viz. axinite, epidote, melanite, lapis lazuli, 

 scapolite, and tourmaline ; and we also find beds of limestone 

 converted into anhydrite and gypsum, apparently from the sul- 

 phurous fumes which have accompanied the diorite eruptions, and 

 which also appear to have been a main agent in the production 

 of much kaolin and hydrosilicate of alumina produced from de- 

 composition of felspars ; whilst the lignite beds encountered near 

 dioritic eruptions are frequently converted into true mineral 

 carbon, retaining the burnt woody structure, or into anthracite. 



(8) Minerals of the Post- Silurian Auriferous Granite Erup- 

 tions, and their accompanying metallic veins. 



This granite here, as well as all over the world where I have 

 studied it, is invariably composed of orthoclase, Muscovite, and 

 quartz, with particles of gold and iron pyrites disseminated oc- 

 casionally throughout it ; at its points of contact with other 

 rocks through which it has forced its way it often contains tour- 

 maline and hornblende, as well as occasionally scapolite ; and 

 when the granite is in greatly preponderating mass in relation 

 to the metamorphic strata, we sometimes find it appearing as 

 hornblendic granite for some considerable area, apparently from 

 the absorption of more or less of the strata in question ; 

 normally, however, it is a compound of only orthoclase, Musco- 

 vite, and quartz. The minerals which it carries along with it in 

 Chile are almandine, chalcopyrite, gold, graphite, iron pyrites, 

 magnetite, iron-glance, traces of pyrrhotine or magnetic pyrites, 

 marcasite, and to which possibly we may add eucairite, and 

 traces of rutile and cupriferous Scheelite*. 



As secondary minerals, we find calcite, chalybdite, Chileite, 

 dolomite, Gothite, Limonite, and quartz. 



(9) Minerals of the Metamorphic Rocks of Pre-Devonian Age. 



These are but few, and are almandine, common garnet, 

 hornblende, graphite, phlogophite, Muscovite (?), quartz and 

 talc ; and at the points of contact with the granitic eruptions, 

 we find tourmaline, epidote, and chiastolite. 



* A selenite (eucairite?) is reported from Port Flamenco, where granite 

 occurs, and also from a locality in the back Cordilleras of Coquimbo. I 

 have placed it in this group, as I found the selenides of Cacheonta near 

 Mendoza pertained thereto. Rutile is found, but in mere traces, in the 

 granite of the coast ; and the cupriferous Scheelite was discovered by Do- 

 meyko in small quantity in the Llamuco copper vein which cuts through 

 the granite of Illapel. 



