.272 THE CANADIAN NATURALIST. . [Vol. Vl. 



rocks first dessrves mention in this connection. Felspar crystals 

 are frequently found in granites, broken in two pieces, these frag- 

 ments baing displaced, and the space between them filled up with 

 granitic sub;stanc3. This is the case with the orthoclase crystals 

 of the porphyry of Elba and of the quartz poryhyry of Ihnenan ; 

 with the sanidine in the trachyte of Drachenfcls, and with 

 the tourmaline of the granite of Winkelsdorf in Moravia. These 

 phenomena serve to prove that the solidification of original rocks 

 took place very gradually, and that their crystallisation was in 

 progress long before they became completely consolidated. 



Very many of the facts recorded regarding the occurrence of 

 accessorial minerals in rocks go to prove that they w^ere the first 

 to separate from the fluid magma and assume their characteristic 

 forms. Blum has observed that the long tourmaline crystals 

 which occur in the chloritic schists and granites of Aschoffen- 

 burg and of Winkelsdorf in Moravia, and which are frequently 

 found fractured, have their S3parated fragments frequently bent 

 out of their proper direction and cemented together by mica. 

 The proof here seems plain as to the formation of the tourmaline 

 prior to that of the mica.^ In the large grained granite of Berg- 

 stiege, near Ruhla in Thuringia, Senft has observed that the 

 quartz partly surrounds the tourmaline and wholly surrounds 

 the mica plates, and regards this occurrence as proving that 

 the formation both of the tourmaline and of the mica preceded 

 that of the quartz. f Very many instances have been observed 

 which go to prove the formation of tourmaline prior to 

 quartz, and not a few from which it may reasonably be inferred 

 that it crystallised before both mica and felspar. In con- 

 nection with the ore deposits of Scandinavia, mention is made 

 of the occurrence of iron pyrites completely enclosed in a crystal 

 of tourmaline. A similar relation has been observed in the 

 case of garnet, w^hich very frequently encloses in its crystals a 

 kernel of mao-netite. Garnet is, however, noted for enclosing: 

 many other minerals, quartz, mica, iron glance, vesuvian, epi- 

 dote, copper pyrites, iron pyrites, galena, blende, and especially 

 hornblende varieties, having been found in the interior of 

 its crystals. According to Blum the orthoclase crystals of the 

 porphyrite of the Baranco des las Angustias, on the Island of 



• Ziikel, Pctrographic; I, es. 



t Die Krystaliinisclie Fclsgeracntheile, p. 512, 



