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BOOK VI
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119
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ble
rough rocks commonly, according to Pliny, hang from a rope. It is also
found in metalliferous veins and veins of the pure mineral. It occurs
in many places, in Spain, France, Germany, the Alps, Scythia, Cyprus,
Asia, Carmania, India and on two islands in the Red Sea near Arabia,
one island being called Neron, the other Chitis.
The
best quartz is colorless and as transparent as limpid water. Flaws are
common, those that have a color are spotted or similar to black clouds
while those that have a body resemble scales, "salt," ulcers, hairs,
rust, iron rust and lead rust. Sometimes quartz crystals contain silver
minerals of a lead or reddish color (probably argentite and proustite).
The former is the more valuable and the best. The silver is usually in
the body of the quartz, rarely on the end.
Quartz
crystals vary in size and consequently in weight. While the shortest
crystals may be less than half an inch high Juba writes that he
remembers a crystal eight inches long that was dug up on the island of
Chitis by Pythagoras, prefect of king Ptolemaeus. Crystals may be less
than a quarter of an inch thick yet Pliny describes a crystal found in
India that was so thick that a vase which could hold three quarts of
liquid was cut from it. Xenocrates describes a vase similar to an
amphora cut from a single crystal. While the smallest crystal may weigh
only a scruple, Pliny writes that Livia Augusta placed one in the
temple to Jupiter which weighed approximately fifty pounds.
Quartz
crystals are rarely found single. Usually a number occur together
growing from a common base, sometimes standing up separately,
sometimes united. Some crystals stand vertically, some are inclined,
some lie on the base adhering to it so that they cannot be removed
easily. Sometimes a number grow on a common base and are so united
that they can only be separated with the greatest difficulty. A single
large and perfect crystal may form surrounded on all sides by many
small and imperfect crystals which are seen to have only three sides as
if they were half crystals since quartz is hexagonal although the sides
are usually unequal. Quartz crystals often have two broad and four
narrow sides while rarely there are four broad and two narrow sides.
Moreover a narrow side may taper and a broad side become broader.
The
sharp termination of the crystal is hexagonal similar to the body. The
point differs in that the narrow pyramid is not always above the
narrow side and sometimes the broad pyramid may be above the narrow
side. Only a small portion of the mass of the crystal is in the point,
the greater part being in the angular body although some crystals found
on the cliffs of Blocheberg have a large point and a small body. The
faces of the point are so much smoother than those of the rest of the
body, unless they contain flaws, that they can be polished only with
great effort.
Since
quartz cannot withstand heat, cold liquids can be poured into quartz
goblets without injury to them but if a hot liquid is poured into them
they break. Not only are goblets made from this mineral, such as
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