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204
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DE NATURA FOSSILIUM
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fourth
since minerals containing an earth and a metal are sometimes as hard as
stone. As regards translucency, minerals of the second genus are not
translucent since neither earth nor metal is transparent. Thus
transparent minerals must belong to the other three genera. The proper
one is determined by smelting. Minerals of gold, copper and other
metals are classified in the same manner.
Species
of these genera are usually classified by color. One genus embraces
many species, another few, as I shall explain presently. Since the
species of the silver minerals are better known to our miners than
those of the other metals I shall consider them first. There are
lead-colored, gray, black, white, red, purple, liver-colored, and
yellow silver minerals. The lead-colored mineral whose name we derive
from plumbum, is known to the German miner by a name derived from glass.2
Actually it lacks the true color of galena and is not transparent as is
glass from which the name is seen to have been derived. Sometimes it is
the color of galena although darker. The two are similar but anyone
acquainted with mineral substances can distinguish one from the other
by eye. Nature has produced this mineral from a large amount of silver
and a small amount of earth. Galena, composed of lead and stone,
sometimes contains silver. The two have distinctive features. Galena
can be pulverized with a pestle in a mortar while argentite flattens
out. When galena is struck with a hammer or knife or compressed between
the teeth it flies apart while argentite spreads under the flow of the
hammer, can be cut with a knife and is compressed between the teeth.
There is a hard silver mineral belonging to this same species that
cannot be distinguished from galena by eye but only by smelting.
However, it is readily recognized by experts. Whether a mineral
contains a metal and stone, or earth is determined by smelting, as I
have said. If it contains stone it is usually a lighter color. Both the
hard and soft silver minerals have their characteristic true color
inside while on the outside they may be black, yellow, or some alien
color. Hammering immediately brings out the true color.
Native
silver takes first place, argentite second. Ninety pounds of silver is
obtained from one hundred pounds of the purest mineral.3
From this we know that the pure mineral contains less than a tenth part
of earth since some of the silver is burned away and some goes into the
slag. This mineral is uncommon at Rhetia, Noricum, and Dacia, and
common in Germany although it is not found in all the silver mines. It
is most abundant in Misena at Schneeberg, Scheibenberg, Garium,
Marienberg, Annaberg; in Bohemia at Abertham in the Joachimstal valley
and in nearby mines. Sometimes a portion of a vein is twenty-four to
thirty or
2 Latin, argentum rude plumbei coloris; German, glaserze; English, argentite, silver sulphide.
3 Pure argentite contains 87.1% silver and is often more or less intimately associated with native silver.
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