134 OR VILLE A . DERB Y 



with a light green tinge. Lower down we came to the middle 

 or second body. Here the 'taua' (feldspathic clay) was stiff 

 and sandy, marbled with a fat, blue, muddy marl, which leaves 

 upon the fingers a greasy, steely streak. It also yields a dark 

 olive-green argile harder than the rest ; like all the others it has 

 consistence in situ, but when removed it crumbles to pieces after 

 drying. Lieutenant-Colonel Brant gave me from this corpo a 

 fragment of hard, large-grained clay, reddish colored with oxide, 

 and showing a small brilliant imbedded in it. We then descended 

 to the lowest formation. Here the clay contains very little sand, 

 and much stained ; the colors are white and blue, red and yellow, 

 rosy, spotty, and in places dyed as with blood. Here also are 

 found the 'Agulhas' in streaky bundles of iron-like asbestos. 

 The sole of the pit is uneven with working, and in places ' horses,' 

 ' old men,' and long walls of stiff clay have been left standing 

 amongst the holes and gashes. From this point the several 

 lodes are distinctly traceable in the walls of the basin." A 

 more technical description is given by Gorceix 1 as follows : 

 " One of the beds of bluish black color is composed of clay 

 impregnated with oligiste in small fragments with rutile and 

 anatase ; the second of lithomarge with entire crystals of quartz 

 having the same aspect as those of the topaz mines [near Ouro 

 Preto]; the third and most important, with a thickness of more 

 than 1.50 111 , is composed of a series of beds of mottled clay. The 

 stratification planes, parallel to those of the quartzites, are still 

 clearly visible ; the layers are undulated, folded like those of the 

 intact schists that are found a few meters distant. Fragments 

 of schist still almost intact occur in the midst of the clay. These 

 beds of clay are traversed by small veins of quartz, granular or 

 in bipyramidal crystals, oligiste and rutile, showing no signs of 

 wear. Octahedral oligiste is found in certain points in extreme 

 abundance impregnating the rock ; in other points it is substituted 

 by ordinary oligiste. The aspect of the gravel resulting from 

 the washing of this clay is entirely different from that of the 

 alluvial deposits, though composed of the same elements. The 

 1 Comptes Rendus, 1881. 



