Book III about halite and nitrium, alum and acrid juices and related minerals, sulphur, bitumen, realgar, and orpiment; the fourth, chrysocolla, aerugo, caeruleum, ferrugo

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	46	DE NATURA FOSSILIU Μ

	and rarely produced artificially while the latter is common in nature and equally common as an artificial mineral. There are two genera of the liquid, one is pure, the color of milk, limpid, and may smell of fire. This variety is widely used because of its purity and is called φορίμητ by the Greeks. The other genus of liquid is impure, light colored and cloudy and because it is fouled and polluted with foreign matter is called παράφορος. The latter liquid is even adulterated with very fine rock fragments and tinted with oak galls. The solid mineral occurs in a variety of forms. Since it has been named σχίσκ by the Greeks it has a cleavage. It occurs in lumps and as a type of "flower of alum." This type not only exudes from and grows on veins but also on atramentum sutorium when they both occur in the same vein. Pyrite, having been altered, is the parent of both minerals. The mineral which can be cleaved either has been compressed and compacted like a lump or it has effloresced in the form of individual whitish-gray hairs. These are called τριχΐτ« by the Greeks, capillaris by the Latins. Alum may be spherical and this is called arpwyyvXos. There are three species of this form, one which is puffed up like a bubble, another full of pipe-like openings similar to some sponges, while the third is solid. A variety which has the shape of a heel is called άστραγαλω-ros and that in the form of a brick πλινθιτκ. The mineral which occurs in crusts is called πλακίτι? by the Greeks. Today it is made in the form of cones from lumps of any kind and this is called saccharinus. Nature has given alum a variety of other distinctive qualities. The color may be either white, grayish-white, or, if in fairly good sized pieces, a dark color which is called black. The best quality is white and dark colors are rare as Pliny has written. It may be reddish white as is that which comes from the Neapolitan region or light colored as the rounded and fibrous mineral mined at Schachic, Bohemia. The artificial mineral is usually more transparent than the native alum. Since the latter is not so dense all tenuous alums are not translucent. Regarding taste, alum is strongly astringent and for that reason is called στυπτηρία by the Greeks. Regarding the odor, not only the liquid, which has the strongest odor, but also the dry mineral gives off an odor of fire not unlike that given off by stones when struck together. On the other hand the artificial mineral has no odor. The capillary mineral is the softest and most fragile, next hardest is the material that resembles bubbles and that which is porous with a pipe-like appearance. The next hardest is the material that resembles a heel. All the rest are dense and hard, for example, all artificial alums and the native mineral that occurs in the form of blocks, in tabular crusts, and in all other solid forms. Liquid alum is very unctuous, the artificial mineral only slightly so. Some alum is dense, as that congealed from a liquid while some is tenuous such as that which occurs in the form of bubbles or is very porous. The alum that resembles a heel is tenuous since it too is porous. When the mineral is

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