Anniversary Address. 19 



The Cascalhao of the old watercourses goes by tlie name of 

 Guipara ; that at the heads of rivers Tabuleira ; and the partly 

 rounded pebbles of the present streams are denominated Gorrido. 



The assemblage of all tbe minerals associated with th.e diamond 

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

 terms are taken, called " the 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 with sub-oxide of iron — 

 Eutile 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 chromate of 

 lead are met with. Scorodite and pseudomorphs of the same 

 also occur in the schists and in the " ta^alian-canga." Amethyst is 

 found in veins in schists and gneiss, whilst Chrysolite, Cymophane, 

 and green Tourmaline collect in the Cascalhao of the crystalline 

 schist rivers. 



Mr. Heuland, in 1823, exhibited to the Geological Society of 

 London ( Transactions, second series 1, p. 119 ) a diamond in 

 cascalhao surrounded by Scorodite (a cupreous arseniate of iron), 

 which I do not see in M. Damour's lists, but which was found 

 by Eschwege ; and Dana says it encrusts quartz and beryl, and 

 is found in Victoria with gold and Arseno-pyrites. Of the latter 

 mineral Mr. Ulrich gives three localities. It has not yet been 

 found on the Cudgegong, But Schorl rock does occur there, 

 and in the sands of Bahia, at Diamantina, in Minas G-eraes ; and 

 this mineral there called Feijao, as well as Hydrophosphate of 

 alumina, is considered an indication of diamond; 



