Theophrastus and Mucianus are of opinion that there are certain stones which bring2683 forth other stones. Theophrastus states, also, that a fossil2684 ivory is found, both white and black; that the earth, too, produces bones, and that osseous2685 stones are sometimes found. In the vicinity of Munda in Spain, the place where the Dictator Cæsar defeated Pompeius,2686 there are stones found, which, when broken asunder, bear the impression of palm leaves.2687

There are some black stones, also, which are held in much the same esteem as the marbles; the Tænarian2688 stone, for example. Varro says that the black stone of Africa is more durable than that of Italy; while, on the other hand, the white corani2689 are harder than Parian marble. He states, also, that the silex of Luna admits of being cut with a saw; that that of Tusculum decrepitates in the fire; that the tawny silex of the Sabine districts, with the addition of oil, will yield a flame even; and that, at Volsinii, molar stones2690 for grinding are found. Among the prodigies that have happened, I find mention made of millstones that have moved of themselves,