- The lapidariesploy a considerable qua ntity of diamond in powder, which they use with steel instmments to divide pebbles and preeioua stonos. The small pieces of diamond of which the powder is made. are worth 23 shillings a carat. The use of the diamond in this way is Very extensive. Had nature withheld the diamond - the pebbJe, the agate, and a variety of other stones, would have been of little valuÃ©is no other substance is hard enough to operate upon them. In this way, rock crystal from Brazil is divided into leaves, and ground and poli8hed with diamond dust for spectacles and oiher optical inctruments.