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108
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DE NATURA FOSSILIUΜ
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Mysia.
It is quarried at the town of Confluentia, so-called because it is at
the confluence of the Moselle and Rhine rivers. It is found in Lower
Germany near the famous town which takes its name from waters. Since
pumice is as full of open channels as a sponge it is called lapis spongia, according to Vitruvius. It is called κίσσηρπ by
the Greeks. This name, according to certain writers, comes from the
name of the worm that eats grain and is called /as by the Greeks and gurgulius (weevil) by the Latins. It makes holes in the grain until it has the appearance of pumice. Theo-phrastus called the rock halcyonium because he thought it had congealed from sea foam but we have already discussed this mineral.
There
are varieties of pumice. They are not all of one color since they may
be black, gray or white. Some are so soft they can be ground to a sand
in the hands, for example, that found on Nisida, according to
Theophras-tus. Others are hard. All are porous and light because of the
internal cavities filled with air. Due to its porosity it will float
on water as do other pumaceous stones no matter how large they may be.
A pumaceous stone of this lightness is found on Thyrrae and another on
the island of Nisida and these may be true pumice. Pumice which floats
when whole will sink when crushed. Although all are light and porous
the black varieties are denser and heavier while the white and gray
varieties are lighter. Although it contains a large amount of air it
will neither take fire nor burn because it lacks moisture. The force of
fire destroys it. Because of its roughness pumice is cleansing and
women use it chiefly to beautify the skin and for thinning hair. Both
men and women use it as a dentifrice and men use it for many other
purposes. Transcribers smooth books with it. Physicians mix it with
substances that produce flesh. When wine workers put in it casks of new
heating wine the heating ceases immediately. The drinkers in a drinking
contest take a powder of pumice but Theophrastus warns that this is a
dangerous practice unless they become satiated with the immense
draught. Physicians prefer that which is white, rather light, porous,
harsh, fragile and free of stones.
Finally
I shall discuss the remaining stones—those to which we have given names
which come from the fact that when thrown into a furnace they liquify
with ease and flow freely. There are three genera of these, one similar
to transparent gems and a second that does not resemble gems. The
latter is not transparent as a rule, rarely partially so. The former is
found in small quantities in silver and other mines. The latter is
found in veins characteristic of the mineral and often in abundance.
Material of the third genus is used in making glass although glass can
be made from the other two genera. Small pebbles of the first genus are
not only transparent but brilliant and with the same colors as those
found in gems. Some of the pebbles resemble quartz, others smaragdus, prase, sapphire, amethyst, hyacinthus, carbunculus, chrysolithus and other gems. However they are markedly different from gems in degree of hardness. If we
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