"The 'mixed' minerals, which are composed of those same simple minerals, differ from the 'compounds,' in that the simple minerals each preserves its own form so that they can be separated one from the other not only by fire but sometimes by water and sometimes by hand. As these two classes differ so greatly from one another I usually use two different words in order to distinguish one from the other. I am well aware that Galen calls the metallic earth a compound which is really a mixture, but he who wishes to instruct others should bestow upon each separate thing a definite name."
For convenience of reference we may reduce the above to a diagram as follows:
{ { Earths { (a) Simple { Solidified juices { minerals { Stones { { Metals { A. Homogenous { { bodies { { { (b) Compound { Being heterogeneous mixtures { { minerals { of (a) { 2. Mineral { bodies { { { B. Mixtures. Being homogenous mixtures of (a)
[5] _Experiendae_--"a trial." That actual assaying in its technical sense is meant, is sufficiently evident from Book VII.
[6] _... plumbum ... candidum ac cinereum vel nigrum_. "Lead ... white, or ash-coloured, or black." Agricola himself coined the term _plumbum cinereum_ for bismuth, no doubt following the Roman term for tin--_plumbum candidum_. The following passage from _Bermannus_ (p. 439) is of interest, for it appears to be the first description of bismuth, although mention of it occurs in the _Nützlich Bergbüchlin_ (see Appendix B). "_Bermannus_: I will show you another kind of mineral which is numbered amongst metals, but appears to me to have been unknown to the Ancients; we call it _bisemutum_. _Naevius_: Then in your opinion there are more kinds of metals than the seven commonly believed? _Bermannus_: More, I consider; for this which just now I said we called _bisemutum_, cannot correctly be called _plumbum candidum_ (tin), nor _nigrum_ (lead), but is different from both and is a third one. _Plumbum candidum_ is whiter and _plumbum nigrum_ is darker, as you see. _Naevius_: We see that this is of the colour of _galena_. _Ancon_: How then can _bisemutum_, as you call it, be distinguished from _galena_? _Bermannus_: Easily; when you take it in your hands it stains them with black, unless it is quite hard. The hard kind is not friable like _galena_, but can be cut. It is blacker than the kind of _rudis_ silver which we say is almost the colour of lead, and thus is different from both. Indeed, it not rarely contains some silver. It generally indicates that there is silver beneath the place where it is found, and because of this our miners are accustomed to call it the 'roof of silver.' They are wont to roast this mineral, and from the better part they make metal; from the poorer part they make a pigment of a kind not to be despised."