APPENDIX, 49 



sandstone into Itacolumite has also aflected the diamond crystal- 

 lisation. Eor a long period the red Psammite and the secondary 

 Itacoliimite sandstone have been regarded as the sole matrices 

 of diamond, whence it has been derived by the detrital erratic 

 deposits ; but since then it has been found in the true Itacol- 

 umite, subordinate to the talc schists with quartz. 



The diamonds in the derived deposits are more numerous the 

 nearer the deposits are to the solid rocks. 



The detrital beds are classified according to their character. 



Thus Crroiqnaj'a is a drift not due to the present system of 

 drainages. Btirgallio or Giirgallio consists of superficial frag- 

 ments of underlying rock. The decomposed schist of the latter 

 is called Barro. A sandy mass between these is spoken of 

 as Terra. Another bed of granular Itacolumite is known as 

 Fizarro ; but all belong to the decomposed rocks. 



Casealho represents the sand, clay, and pebbles in the beds of 

 rivers, torrents, lakes, and of the hollows in their courses through 

 the solid rocks. Taho-canga or Ta])aJian-canga is what we call in 

 Australia cement. 



The Casealho of the old watercourses goes by the name of Gut- 

 para ; that at the heads of rivers, Tahuleira ; and the partly 

 rounded pebbles of the present streams are denominated Gorrido. 



The assemblage of all the minerals associated with the diamond 

 is, according to Heusser and Claraz, from whom the last four 

 terms are taken, called " tlie formation.^'' 



We learn further from these authors that though diamond 

 belongs undoubtedly in Brazil to Itacolumite and Metamorphic 

 schist, yet it is not so necessarily ; for the Itacolumite mountains 

 do not always contain diamond, and in that of Itacolumi itself 

 none are found. 



The minerals seem to follow a choice as to their matrix and 

 associations. Thus anatase occurs V\dth sub-oxide of iron — 

 rutile and brookite. Euclase is found with topaz, in a whitish 

 clay of decomposed rock. 



Specular iron ore, rutile, black tourmaline, hyaline and smoky 

 quartz are associated. Topaz (sometimes "rotten") is abundant, 

 but is no longer, in comparison with euclase, an object of search. 



Ores of tellurium, as well as sulphur, occur in some localities. 

 In the crystalline schists, crystals of lime, arragonite, magnetic 

 iron pyrites, copper pyrites, manganese ores, and chromata of 

 lead are met with. Scorodite and pseudomorphs of the same 

 also occur in the schists and in the '"''tapalian-cangaP Amethyst is 

 found in veins in schists and gneiss, whilst chrysolite, cymophane, 

 and green tourmaline collect in the Casealho of the crystalline 

 schist rivers. 



