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DE NATURA FOSSILIUM
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of
argentiferous, three species of plumbiferous, cupriferous, or
ferruginous stone. The Greeks are seen to have called these earths
containing a mixed substance by the same names as the above mentioned
metallic earths. I shall consider these substances briefly and mention
only the argentiferous varieties. An earth may contain mixed silver
minerals that are either lead-colored, red, white, black, gray,
liver-colored, purple, or yellow. I should mention that an earth may
contain such mixed substances as galena, pyrite, or cadmia of
the fourth genus. The combinations may vary since the particles may be
the size of walnuts, beans, peas, algaroba seeds, or even so small that
no metallic substance is left when the earth is panned. Miners
distinguish earths that contain mixed substances by color.
Sometimes
particles of species of the sixth genus are contained in an earth or
adhere to it. If the earth contains sulphurous or atramentous pyrite,
atramentous cadmia, or some other species, it will, of course,
change the composition. Particles of species of all six mixed genera
may adhere to or be enclosed in a congealed juice, stone, or metal.
Compounds that contain more mixed than simple substances are different.
These inÂclude species of the six mixed genera that enclose or have
adhering to them particles of earth, congealed juice, stone, or metal.
There
remain the compound substances containing three substances. These may
be three simple, three mixed, one simple and two mixed, or two simple
and one mixed substance. Furthermore, compound substances may contain
four, five, and even as many as ten natural substances and these give
rise to great numbers of species.
The
philosopher takes pleasure in the contemplation of the nature of these
compounds while the miner takes pleasure in the profit and use he
obtains from the metals he extracts from them.
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