Diamonds are also found, as I have remarked, in the crust or external covering of mountains. These masses are formed of a bed of ferruginous sand, with rolled flints, forming an ochreous pudding-stone, from the decomposition of emery and muddy iron-ore; it is called _cascalho_, and the beds, or strata, _taboleiros_. These _taboleiros_ have different names, according to their situation or their nature. When the stratum is horizontal, and in the plane of the bed of the river, it is properly called a _taboleiro_; but if it rises in banks, it is called _gopiara_: lastly, if the pudding-stone contains much emery, it is then denominated _tabanhua cauga_ in Brazilian, that is to say, black-stone or iron-stone. In some places the _cascalho_ is uncovered, in others, it lies beneath a kind of vegetable muddy earth, _humus damascena_, _Linn_, or beneath a reddish fat sand, which sometimes contains roundish flints. This happens in the returns of the mountains, or upon the banks of great torrents. This sand is called _pisarra_. The bank, or stratum beneath the _cascalho_, is either shistus, rather sandy, or the solid bog-ore of iron. It is likewise in the _cascalho_ that gold in spangles and in pyrites is found; the former of which is, in my opinion, afforded by the decomposition of the auriferous pyrites; for the gold in veins has another form, and its matrix is either fat quartz, or fine grained tender _cos_, micaceous gneis, or the quartzose ore of iron, _tophus ferreus_. Linn. The exploring of diamonds is performed by changing the beds of streams, in order that the sand or gravel may be washed, and the diamonds selected; or by breaking the _cascalho_ with large hammers, and afterwards washing it in troughs. This washing differs from that of gold, because it requires a small quantity of very clear water, and very little of the _cascalho_ at a time; proportions, which are precisely contrary to those required in washing gold. Black slaves are employed in this business, entirely naked, excepting a cloth round their middle, in order that they may not embezzle any of the diamonds; but in spite of every precaution, and the vigilance of numerous inspectors, they nevertheless find means of concealing them, which they sell at a very low price, to the interlopers, for tobacco and rum. _An estimate of the Sums produced to the Portugueze Government from the Brazil Diamonds._