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10
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DE NATURA FOSSILIUM
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and unctuous dissolves slowly as does halite, nitrum, alum, and atramentum sutorium. Artifical minerals dissolve quickly. The same is true of natural efflorescences of halite and nitrum. These
minerals do not occur within the earth. Bismuth, tin, and lead melt
quickly in a fire; the other metals with greater difficulty; iron with
the greatest difficulty. Stones similar to gems melt more quickly than
true gems. Minerals which dissolve in a liquid almost never melt in a
fire but are either reduced to a powder or consumed, as I shall discuss
a little later. On the other hand, minerals which melt in a fire are
not soluble in liquid.
Some
minerals such as earths, certain stones, and sulphur become soft in a
liquid and iron and copper become soft in a fire. Those minerals which
become soft in a fire and correctly called μαλακτά by the
Greeks since they can be worked so that, with one blow of the hammer,
the surface is spread out and at the same time lowered. However
minerals which are softened by a liquid are not called μαλακτά for
although they become soft they cannot be flattened or stretched like a
sinew, membrane, or piece of leather without breaking. Some of the
latter minerals become soft quickly, for example the earths, while
others, such as hard stones, soften slowly. All minerals which are not
softened in a fire can be softened by water. For example, a portion of
the hardest marble buried within the earth may be softened by water
while the rest retains its hardness.
Some
minerals are damp such as earths and sulphur, while metals and
transparent gems are not. Damp or moist minerals are those which
become soft when sprinkled with water. Halite, nitrum, alum, and atramen-tum sutorium are
not moist since they dissolve instead of softening when sprinkled with
water. Since all minerals contain earth and water those which dissolve
or soften in water consist mostly of earth and those that soften in
fire contain an abundance of water. Some minerals are pliant and sticky
such as soft bitumen. Some are so coherent that when drawn out it is
difficult to separate them from the parent mass. Similarly, unctuous
earth which has been softened with water is sticky and, as the poet
affirms,
"It sticks to the fingers like pitch"2
Certain minerals, having been crushed, are broken down with ease in water. These are called ψαθυρά by
the Greeks. Meager earths belong to this class and many varieties are
found in mines. A few minerals are flexible, namely asbestos, the only
mineral that is spun and woven, and metals that occur in arborescent
shapes. If these wires of native metals are straight they can be bent
in any direction, and if bent they can be straightened. Other minerals
can be neither straightened nor bent.
Most
minerals are friable, i.e., they can be pulverized by either pounding
or grinding them in a mortar. A very few are cleavable, i.e., capable
of being split into two parts such as talc which occurs as tabular
aggregates.
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* Virgil.
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