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Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth

Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth Page of 251 Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth Text size:minus plus Restore normal size   Mail page  Print this page
210
DΕ NATURA FOSSILIUM
Bohemia, and from other mineral they obtain from thirty to sixty pounds.18
Minium secundarium (red lead oxide) and spuma argenti (foam of silver) are made from plumbarius lapis (galena). I have discussed the latter in the preceding book. Secondary minium is made in the following man­ner. Plumbarius lapis that contains little or no silver or plumbaria arena with a color similar to galena is heated in a furnace until red hot. It is then ground to a flour and sieved, the coarse material being reground. This minium can be made from galena that contains appreciable amounts of lead and silver. In separating silver the associated metal is lost and during the destruction of the lead the silver collects together so it is not important. Sandyx which closely resembles this minium is made from cerussa that is made from lead. Since there is a good profit in making minium it is often adulterated with secondary minium, sandyx,19 and syricum.i0
Plumbarius lapis and plumbaria arena have the same properties as lead slag. Silver-free galena and plumbarius lapis are bright with a lustrous black color. Lead slag that is free of silver and lead, is the same color as the two minerals mentioned above. When this slag is thrown into the same furnace with these minerals it destroys a portion of them.21
18 Galena contains 86.6% lead.
19 Both minium secundarium and sandyx were artificial minium.
20 Syricum was a mixture of lead and iron oxides.
21  Agricola discusses these various materials at length in Bermannus, pages 433-436. The following excerpts are significant.
Naevius. "... there is still one thing that bothers me.
Bermannus. "What is it? I shall see if it is possible to explain it.
Naevius. "Dioscorides writes that his mineral molibdaena found at Sebastia near Corycos is golden-yellow and brilliant yet the mineral you show me has a certain brilliancy but is lead-gray and by no means golden-yellow.
Bermannus. "Of course I could repeat what I have already said about the galena of Pliny that he himself says is called molibdaena and my conclusion would in no manner be weakened but, because, up to now you have apparently wished it, I shall say just what I believe and then you are at liberty to agree or disagree with it. This galena that is the color of lead is called by Dioscorides, if I am correct, μο\φδοαδή? Xifos because it is a species of lead and differs from the native lead mineral molibdaena of Dioscorides himself more in color than com­position."
Naevius. "Then what is your conclusion about plumbarius lapis"! It may be, by chance, a species of lead (plumbum) since these have, essentially, the same appear­ance and color and are, in general, of the same composition. Is it not true that certain people fashion gems today from glass that are so similar to the natural stones that very often they deceive the unwary? Experts can prove that they are not gems but glass through the use of the file and fire.
Bermannus. "That is true and indeed there are many other substances that very often have a deceptive appearance. But it is obvious from the writings of Dio­scorides himself that plumbarius lapis contains plumbum which, he writes, has
Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth Page of 251 Book X lapis sabinicus, lapis selentinus, lapis liparaeus and other mixtures of stone, metal and earth
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