12 A Book of Precious Stones
rather than for personal decoration. As examples of such stones may be cited the Agate, Malachite, and Rock-crystal.
Max Bauer, in his great work on precious stones, discusses in a very
interesting way the motives of mineralogists and jewellers in group,
ing and classifying gems, and seems to regard each as perfectly
justified from their different view-points. As an example he cites the
classification by K. E. Kluge, the German authority, as used in his Eandbuch der Edelsteinkimde, published
in 1860, wherein Kluge distinguishes five groups of precious stones,
characterised by their value as gems, their hardness, optical
characters, and rarity of occurrence. It is interesting to note also
that, according to Bauer, Kluge was dominated to a large extent by the
then market value of the stones, probably in Germany, or in the
European markets in general.
1. True Precious Stones or Jewels
characters are: great hardness, fine colour, perfect transparency
combined with strong lustre (fire), susceptibility of a fine polish,
and rarity of occurrence in specimens suitable for cutting.