Book I Minerals color, taste, odor , physical properties of gemstones and minerals such as emeralds, diamonds, rubies, sapphires

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	16	DE NATURA FOSSILIUM

	earths are dug up without careful search. For this reason the former are correctly called μεταλλίυτά, the latter ορυκτά. Such reasoning is weak and unsupported since we do not prospect for metals alone nor at all times. Actually we prospect for gems, veins of well-known earths, and even marbles, while metals sometimes occur as if they were offering themselves to us. For this reason, by neither of these interpretations are these names characteristic of these things even though Aristotle was able to complete his classification. He classifies those stones that do not melt in a fire as minerals and those stones that do melt and contain a metal as "minerals from which metals are obtained" and then he cannot place those stones that melt and yet contain no metal in either of these groups. Actually some of the stones that melt in a fire do contain a metal and are correctly called μβτάΚλβυτά since metals are recovered from them. Other stones contain no metal but having been formed from exhalations melt in a fire and can be poured. These cannot be called μίταλλίυτά. Therefore if all "mineral substances" are formed from vapor, as he himself says, and among all these the ones which have formed from exhalations contain no metal, it follows that there must be three genera of bodies formed within the earth although only two may be formed from exhalations. Philosophers who believed the "earth" to be composed of the three classes, stone, metal, and cultivated earths, are not correct if they mean by "earth," as did Galen, one of the four elements, a body that is exceedingly cold, dry, dense, and heavy. None of these classes is a simple body for all are mixed. But if they visualize, as they seem to, a body of such combination that the earth surpasses the other elements in weight, they do not see that there are more than these three classes of it. Many forms of such an earthy body are found in living matter such as bones, nails, claws, and shells. Actually there are as many parts of trees and shrubs that are earthy as there are forms of earthy matter, the bark, the wood, the inner bark, the shell and kernel of the nuts, bunches of grapes, and many others. Thus, even if they regard the forms mentioned above as higher forms which are parts of living matter, they still hold that there are three forms of inanimate matter, namely, stone, metal, and earth that is cultivated. But since philosophers have not considered it necessary to classify things in this way, the Peripatetic philosophers force them with this doctrine. Metals contain more water than earth. In which case, even though those philosophers may not be willing to yield to the Peripatetic philosophers nevertheless none of them can place congealed juices and especially mixed bodies in one of these three genera. Even Avicenna himself, although he increased the number of classes, was unable to classify red ocher and other well-known earths that do not contain a metal. Then, since certain stones that contain no metal melt and flow in a fire, he correctly distinguishes stone and metallic material, as he calls it, from that which melts in a fire. Finally, without skill but with the capriciousness of chemists he places the two species sulphur and orpiment under sulphureous things. Actually con-

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