In
glancing over the works of Arnault de Villeneuve, of Raymond Lully, of
Paul of Cano-tanto, of Isaac the Hollander, &c, we find a certain
amount of space devoted to precious stones; but no new idea worthy of
note. Thus the end of the fifteenth century is reached* and we emerge
from the medieval age.
Upon
the threshold of the Renaissance a singular character appears, Jerome
Cardan (born in 1501), who furnishes us with some valuable
suggestions. Several works of Cardan, published after his death,
contain some rather absurd passages; but in his treatise De Subtilitate, the careful student finds many ideas which prove that the author possessed great intelligence, and beneath an air of bonhommie a veritable sagacity.
Cardan designates under the generic name of gems all the brilliant stones, and reserves the name of precious stones for
those which are not only brilliant, but rare, and of small dimensions.
These precious stones he divides into three classes: 1st, those which
are brilliant and transparent, as the diamond; 2d, those which are
opaque, like the onyx; 3d, those which are formed by the conjunction
of the two other kinds, as the jasper.
This is very nearly the same classification as that employed by Caire, three centuries after Cardan,
