122 OR VILLE A . DERB Y 



With two exceptions, which will be more fully discussed 

 below, all the known Brazilian diamond washings are in mate- 

 rial — sand and gravel — which has clearly been transported 

 from its place of origin and equally clearly contains the debris 

 of a greater or less variety of rock types, some one or more of 

 which may reasonably be presumed to have a genetic relation to 

 the diamond. As the latter, however, is almost invariably found 

 free in such deposits, or attached to the other elements by a 

 cement, usually limonite, which is visibly of secondary origin, 

 such deposits throw little light on the history of the gem. For 

 the most part these deposits are of quite recent origin, having 

 evidently been formed by the action of the present drainage 

 agencies. In a few cases the gravel has been attributed 1 to the 

 disintegration of conglomerates of various ages, which in one 

 case is presumed to be very great. The age of the gem is thus 

 carried back to a more or less remote geological period, but no 

 other essential addition is made to its history. The concentrates 

 of the rarer and heavier elements of these gravels obtained by 

 the miners in their operations contain many rare and interesting 

 minerals which have attracted the attention of mineralogists, but, 

 thus far, the hopes that have been entertained of tracing the 

 diamond to its original home by means of these satellites, have 

 proved illusive, since none of them have proven to be sufficiently 

 constant to give more than merely presumptive evidence. The 

 few cases that have been reported of diamonds included in other 

 minerals, as iron ores and rarely quartz and anatase, refer to 

 minerals that are known to be readily formed by secondary 

 action, and thus are not necessarily contemporaneous with their 

 inclusions. 2 



The associates of the diamond in these gravels are naturally 

 fragments of all the rocks capable of resisting decay and the 



1 Derby : Am. Jour, of Sci., 1882, XXIV, p. 34. 



2 The specimen described by Eschwege, who attributed great importance to it 

 (Geognostisches Gemalde, p. 430 ; Beitrage zur Gebirgskunde Brasiliens, pp. 213 and 

 341), and which is now in the Heuland collection in the British Museum, is apparently 

 a cleverly executed fraud. The limonite and scorodite of the drusy cavity in which 

 the diamond rests present the peculiar and very characteristic aspect of these minerals 



