BOOK X
	Only the natural substances that are called mixtures and combinations remain. I shall discuss the mixtures first. There are six genera, as men­tioned in Book I. The first genus includes materials that contain stone and some congealed juice; the second, a metal and an earth; the third, equal parts of stone and metal; the fourth and fifth, also a stone and metal but with either the stone or metal in greater abundance; and sixth, stone, metal and some congealed juice. The first genus embraces many species. Nature has produced all of them from stone to which she has added salt, soda, or some other congealed juice. Hence there are as many of these species as there are congealed juices. The number of species is not increased in the same fashion by the different species of stone. In order to describe this genus adequately and at the same time briefly, I must describe some of the material and omit the rest. We have certain distinguishing signs and marks that permit us to identify this genus and determine the juice with which the stone has been mixed. For example, when a stone contains a saline or bitter juice or an astringent or acrid juice, if crushed and placed in water it will give the latter the same taste. A stone that contains halinitrum will decrepitate in fire as does the Tusculian flint of Italy and the white flint from the Carpathian Mountains of Kremnica. When the hardness of this flint is destroyed by the fire it breaks with a noise as loud as that made by the new variety of cannon the Italians call a bombarda. Stone that contains an unctuous juice will burn, those containing sulphur and bitumen burn strongly while those containing realgar or orpiment burn with difficulty. Lapis sabinus, lapis sidicinus, and lapis salentinus from Gnatia contain sulphur and there is an abundance of sulphur in that vicinity. I do not say that you could not find bituminous stone in this same place. The more sulphur a stone contains the lighter the weight, the stronger it burns and the stronger the sulphur odor. On the contrary, the less sulphur a stone contains the heavier the stone, the less it burns and smells of sulphur. Bituminous stones include those found in abundance on the highest parts of the Erineas Mountains; the stone near Bina carried down by the river; lapis liparaeus; the stone found on an island near Lipari; and the stone the Greeks call marithas. Stones which consist entirely of bitumen, such as jet, differ from these mixed substances in that the former are entirely consumed in fire while only a part of the latter is burned. Actually when the bitumen has been changed into soot the stone that remains resembles pumice, especially that from Lipari. One bituminous stone can be distinguished from another since those containing the most bitumen are lighter, burn more readily and have the strongest odor of bitumen, for example, the stone from the Erineas Mountains. On the
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