168 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



them alone, points to the conclusion that it originated in the mineral-veins, as was first 

 insisted upon by Gorceix. This conclusion receives additional support from the fact that 

 Brazilian diamonds, instead of exhibiting a perfect and complete development on all sides 

 such as is characteristic of embedded crystals, frequently show on one side an area by which 

 they seem to have been attached during their growth and development, impressions of 

 quartz-crystals being sometimes seen on such areas of attachment. Moreover, diamonds 

 have been found enclosed in, or attached to, the surface of crystals of quartz, anatase, and 

 haematite, and this could scarcely be explained except on the supposition that these 

 minerals have all grown together at the same time and in the same vein. It has been 

 stated by Gorceix that a few diamonds have in places been met with actually in the mineral- 

 veins themselves, and, though in small numbers, have been extracted ; he compares such 

 occurrences with that of the yellow topaz found near Ouro Preto in quartz-veins penetrating 

 decomposed schists. In these districts, then, the diamond is a vein mineral, while in other 

 localities it is an original constituent of the primitive crystalline rocks. 



The precise method of "winning diamonds adopted in Brazil depends more or less 

 upon the nature of the deposit. A diamond-working is known in Brazil as a servigo, 

 those in a river-deposit being distinguished as " servi^os do rio," while those in valley- and 

 plateau-deposits are distinguished respectively as " servi^-os do campo ^ and " servi^os da 

 serra." The methods in each case have; changed but little during the whole period the 

 deposits have been worked ; the greater part of the labour is performed by negroes working 

 formerly as slaves, but now as freemen. 



In the servicos do rio, or workings of a river-deposit, the first step is the diver- 

 sion of the water in order to lay bare the " cascalho " or diamantiferous material. Only a 

 small portion of the river-bed is laid bare at a time, the operation being effected either by 

 cutting a new channel for the river, or by building a dam in the middle of the stream and 

 parallel to its course, so as to confine the water to a bed one-half its previous width, or by 

 conducting the water away in wooden channels. After removing the barren detritus from 

 the surface of the river-bed so laid bare, the diamond-bearing " cascalho " is dug out. 

 This latter is loose and easily worked, but the " canga," or masses of conglomerate, are often 

 so compact that blasting must be resorted to, and thus the working becomes more lengthy 

 and expensive. 



The work of excavating the " cascalho " can only be pursued during the dry season, 

 from May to the end of September, when the volume of water in the rivers is at its smallest. 

 During these months as much as possible of the diamond-bearing " cascalho ■" is excavated 

 and conveyed to a higher level, being deposited, however, as near the stream or river as 

 safety will permit. In the wet season the level of the river rises rapidly and to a marked 

 extent, thus making the excavation of the " cascalho " a matter of impossibility. At this 

 season the material previously excavated is washed and the diamonds it contains collected ; 

 the place at which the operation of washing is conducted is known in Brazil as a lavra. 



Before the " cascalho " is washed, the larger fragments are separated from the finer 

 material either by hand or by means of a sieve. This fine material is then placed in a 

 shallow, wooden dish of a special kind, knows, as a batea, and agitated in running water ; 

 the lighter and finer portion is thus carried away, and from the heavier remaining part the 

 diamonds are picked out by hand, the process of washing being all the while proceeding. 

 The washers exhibit a wonderful skill in distinguishing the smallest diamonds, such as 

 might easily be overlooked by even a practised eye, from other mineral frao-ments. 



Plate VI. is a picture of the actual working of a Brazilian diamond washing. The 

 negi-oes on the left are standing in the stream and washing the " cascalho " in their bateas. 



