Book III about halite and nitrium, alum and acrid juices and related minerals, sulphur, bitumen, realgar, and orpiment; the fourth, chrysocolla, aerugo, caeruleum, ferrugo Page 57



	BOOK III	45

	on the fields is always as white as halinitrum itself. When the latter is pure it is transparent, salty, slightly acrid, loose-textured and light. It crystallizes in rectangles with pyramidal terminations. It can be crushed with ease. The mineral catches fire easily and burns. It is found in matted masses which contain much air. For these reasons it is useful in making the powder that throws the round missiles of the pieces of ordnance which they call bombard. Both halinitrum and the nitrum that effloresces on walls will take fire.¹⁰ Although halinitrum cleanses, the degree of bitterness differs considerably from that of nitrum. I shall now take up alum (alumeri) which is more closely related to atramentum sutorium}¹ than salt to nitrum. Although all of these minerals are cleansing, salt and nitrum are only slighly astringent, the others, strongly astringent. Atramentum sutorium is more earthy than alum. The two minerals can be separated since alum forms from atramentum sutorium. When the latter is mixed with olive oil alum forms since the oil takes up the earth and one particle of alum unites with another. Also earth alone, thoroughly mixed with water, precipitates alum which gradually crystallizes in cubes. I shall discuss alum first and then take up chalcitis, misy, sory, and melanteria which I will associate with atramentum sutorium since they are related minerals. Alum occurs as a native mineral and is prepared artificially, in both cases forming from water and aluminous earth. There are many alum mines in the world. In Spain it is found in silver mines. It occurs in many places in Germany, near Brambach, Saxony; at Zuenicius and beyond Radeberg, Misena; near Blava and Salfeld, Vogtland; in Bohemia at Schachic half way between Cometavius and Launa. Also in Noricum near the Julian Alps; in Hetruria near the market place named Claudius, at Bassano and Volterra; in Campania at the market place between Pozzuolo and Naples; in Pontus; in Phrygia Hierapolis; in Judea near Mekaur; in Armenia, Babylon, Egypt, and Africa. It is found on the islands of Sardinia, Melos, Strongyle¹² and Lipari. So numerous are the alum mines known to us or mentioned in the literature. Diodorus Siculus states that the Romans obtained the greater part of their alum from the Liparian mines. In Germany it is rarely found pure and is usually produced artificially from aluminous earths, for example, in Hetruria. A few small white hollow pieces the size of a walnut have been found in the moat on the west side of Hildesheim, Saxony. The liquid that comes from Blancheburg near the Harz forest is produced artificially, not by nature, since it is necessary to remove chalcitis or some similar mineral from the latter before it is solidified by heating to produce the pure white alum. Thus all alum is either liquid or solid. The former is common in nature ¹⁰ Agricola apparently includes under nitrum not only various hydrous sodium carbonates but also nitrocalcite, Ca(N0₃)₂ ·ηΗ₂0, etc. ¹¹ This is a general name for iron sulphates. ¹² The alum from this island was known in commerce as "strongyle."