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DE NATURA FOSSILIUM
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forated
in order to make it more attractive by removing the whiter marrow.
When gold is added, according to Pliny, the beauty of this gem is
improved since much of its brilliancy may be lost when it is thick.
I
shall now discuss the form of gems, both the natural form and that
given to them by artisans. There is a great variety of forms. They may
be round like a sphere or hemisphere; sometimes solid, sometimes
hollow. Some are angular and the angles either project or are fiat and
level. When a diamond has a natural hexagonal form, and this is the
most highly prized, it is set in a ring in such a fashion that a sharp
point projects from the setting. If it is oblong or rounded like a
shield it is cut to a hexagonal form, as are all other gems, but the
angular portion is set in the ring while the flat portion stands above
the setting. This form which is given artificially to all transparent
gems is most highly esteemed. The next most popular form is the oblong
gem with facets that are all equally prominent. Lens shaped gems are
less popular. Least popular are gems that are rounded like a shield and
of these the solid gems are more popular than the hollow ones. It is
possible to give a hexagonal form to the solid ones, not to those that
are hollow. In some districts valuable gems are found while in other
districts gems of the same form are valueless. Nevertheless among the
valuable gems some worthless ones are always found and likewise among
worthless gems some valuable ones may be expected.
Since
gems may be classified chiefly by color, I shall speak first of the
(colorless) ones. The Greek name for quartz comes from its close
resemblance to ice and the Latins have translated the Greek name into
their own language and call it crystallus.7 Indeed
certain people believe that quartz is ice, i.e., rain water that has
been solidified by extreme cold, but this is not true. It is actually a
juice that has been congealed by cold. If it were water solidified by
extreme cold it would be most abundant in regions where extreme cold
prevails, where the brooks and even the largest rivers are frozen to
the bottom and it would melt when brought into the warm sunlight. Both
are contrary to facts. Not even the ice on the highest Alps which has
become hard from the perpetual cold which has existed there for years,
actually hundreds of years, is changed into quartz. Even this ice,
although it may be hard as stone, melts when it falls from the heights
into the warm sunshine. We must conclude that quartz is a juice which,
as I have written in De Ortu & Causis Subterraneorum, has
been coagulated by the cold within the earth and for that reason has
been found in openings in marbles and rocks. Sometimes it is turned up
by the plow and it may be carried along by streams but in each case it
has come originally from veins or stringers. Actually, when a crystal
projects outward from the rough rock, as can be observed in the Alps
and the highest part of Mt. Melibocus, it is certain that the force of
the waters has washed away the minerals that were around it. Those who
gather these from inaccessi-
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7 Greek, κρύσταλλοι from Kpbos, icy cold, frost.
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