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BOOK VII
157
has been given the mineral because it flies into splinters when struck a heavy blow with a hammer. According to certain philologists the name is derived from the verb salio,11 not because the mineral possesses any-natural power to fly apart but because it is shattered by fire. Others be­lieve the name comes from the verb sileo12 because they believe the mineral contains within itself a latent fire that is brought to life by the blow of a piece of iron. Among the Germans the name comes from the word "horn" and we call it hornstone.13 Some of the older writers have given this name to marbles, rocks of other genera and mixed stones. M. Varro called Lunan marble "Lunan silex." Vitruvius called hard calcareous rock silex while Varro called this same rock "Sabinian silex." The true silex I am describing is harder than marble and often as brilliant. Since it flakes badly when an iron point is pressed against it, it is not suitable for use in engraving. Since it is hard fire can be struck from it \vith iron with ease.
Silex occurs in both metal veins and in veins composed of this mineral alone. Species are distinguished by color. It may occur the color of horn, white, gray, dark blue, black, brownish red, liver-colored or blue. It occurs on each wall of a vein of jasper at Langovicius. All silex will melt in a fire but only in the hottest furnaces. Otherwise it withstands fire, rain and extreme cold. If it could be dressed with iron tools it would be most useful as a building stone. It is used as road metal and for lining furnaces.
So much concerning stones that are found in veins and stringers. Ac­tually silex and iofus may contain veins and then they should be classed as rocks. Veins spread through the rocks that form mountains. The quarries in these mountains contain many angular masses of rock. This is softer than either gems, silex or marble. It can be sculptured into statues but cannot be polished to a lustrous surface. Even when it is so hard that it can be sculptured only with difficulty it will not take a polish because it lacks denseness. It differs from tofus in weight. It will not melt in a fire but decomposes to a powder and in this way differs from hornstone. There are two genera of rock that can be sculptured. One is rough and makes a harsh sound when rubbed with the fingers. Sand is obtained from the pieces that are cut away during the shaping and for that reason I call it "sandy." The other genus is entirely different and the pieces that are cut away are larger. There are different species of the "sandy" rock that are easily distinguished by color. The white is found at Pirna and Zuicca, Misena; gray at Querfurd, Saxony; yellow at Freiberg, Saxony; red at Rochlitz, Saxony; and a blackish red species at Embach, Saxony. Some is
11 Salio, to leap, spring. The name "salt" is derived from this verb since the min­eral decrepitates when placed on a fire.
12 Siko, to be silent. The verb and the participial noun connote secret or mys­terious.
13 Hornstone, in modern usage, is an impure flint or chalcedony. It is closely re­lated to chert. Flint breaks with a conchoidal fracture and is tougher than hornstone which breaks with a splintery fracture.