Theophrastus and Mucianus are of opinion that there are certain stones which bring[1] forth other stones. Theophrastus states, also, that a fossil[2] ivory is found, both white and black; that the earth, too, produces bones, and that osseous[3] stones are sometimes found. In the vicinity of Munda in Spain, the place where the Dictator Cæsar defeated Pompeius,[4] there are stones found, which, when broken asunder, bear the impression of palm leaves.[5]

There are some black stones, also, which are held in much the same esteem as the marbles; the Tænarian[6] 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 corani[7] 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 stones[8] for grinding are found. Among the prodigies that have happened, I find mention made of millstones that have moved of themselves.