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DΕ NATURA FOSSILIUM
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stones,
and earths do not. Some that burn are entirely consumed such at sulphur
and bitumen while others are only partly consumed, for example spinos. All
that burn, since they are unctuous, produce soot, and, in fact, soot is
obtained from the copious smoke and vapor given off by these unctuous
substances when they are burned.
Concerning
the minerals which do not burn, some can be set on fire: for example,
all metals except gold can be entirely consumed. Some can be melted,
such as gems and the stones similar to gems; and some can be reduced to
a powder, for example, earths and stones moistened with water. Many
gems do not melt in ordinary fires and some stones are hardened, for
example, those found on Siphanto and Como, Italy. Fire can be produced
from pyrite, lapis molaris, flint, quartz, and other hard
substances. Some rocks are hardened by exposure to the sun and air
while others are softened and when moistened by rain, disintegrate.
Vinegar attacks some minerals such as the gem astroites, which our people have named for victory (sigstein) and not uncommonly trochites. When
some minerals are placed in water they swell like a bubble such as
certain earths. Some float on water if whole and sink when broken into
small pieces, for example, pumice, lapis thyreus, and bricks made from pumaceous earth. Galactites, goethite, and hematite yield a juice when pulverized. That of galactites is white; of goethite, commonly saffron-yellow; and of hematite, blood-red. The juice from galactites is sweet while that from goethite and hematite is astringent. Some minerals tint metals, for example, cadmia, iron, copper. If cadmia (zinc
carbonate and silicate) is added to copper it forms brass and if iron
is added to copper it forms white copper. Certain genera of earths and
stones impart their color to anything. White chalk makes white lines,
green chalk called theodotion, green lines, black chalk, black
lines. Silver, although white, makes a black line on wood. Eretria
earth rubbed on copper gives it a violet color. Flint and sandstone
sharpen iron. Lodestone attracts iron while theamedes repels
it. Amber and jet will attract chaff, hair, and straws, while some even
acts as lodestone and will pick up light objects. When flint is used to
sharpen iron it sacrifices something for, during the process of
sharpening, it loses some of its bulk, something is taken away.
Likewise chalk, when used to make marks, sacrifices something and since
it is entirely consumed with repeated use, something is taken from it.
Other minerals have this same property.
Minerals
that are taken in food or drink may be either a remedy or a poison and
possess a characteristic power that accomplishes something while they
themselves suffer some change. Minerals that act as a remedy heal the
body in part through an essence that is characteristic of all such
minerals and in part through some efficacious quality of purity. Some
minerals rich in this peculiar essence counteract poisons, some cure
disease. Others, endowed by Nature with the power of counteracting
poisons cure people ill with the plague. Smaragdus, and Lemnian and Armenian earths have this property. Others counteract a single poison as does lapis-lazuli
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