PERIDOT AND OLIVINE. The mineral "_olivine_" gives us the "_peridot_" (this name should be kept for the deeper bottle green stones), and the olive green gems of this same mineral may correctly be called "_olivine_" or "_chrysolite_." As was explained under garnet, jewelers frequently use the term "olivine" to designate demantoid garnet. The term chrysolite is also sometimes incorrectly used for the greenish-yellow chrysoberyl. FELDSPAR GEMS. Among the minerals softer than quartz, which are used as gems, we have also "_feldspar_," which gives us "_moonstone_," "_Labradorite_," and "_Amazonite_." An opalescent form of chalcedony is frequently gathered on California beaches and polished for tourists under the name of "_California Moonstone_." This name is unfortunately chosen as the material is not the same as that of true moonstone and the effect is not so pronounced or so beautiful. The polished stones show merely a milky cloudiness without any of that beautiful sheen of the true moonstone. "_Labradorite_" is usually correctly named. "_Amazonite_" was originally misnamed, as none is found along the river of that name. The term has come into such general use, however, that we shall probably have to continue to use it, especially as no other name has come into use for this bluish-green feldspar. As has already been said, amazonite is sometimes sold as "jade," which is incorrect. MALACHITE, AZURITE, AND LAPIS LAZULI. _Malachite_ and _azurite_ are usually correctly named, but "_lapis lazuli_" is a name that is frequently misused, being applied to crackled quartz that has been stained with Prussian blue, or some other dye, to an unconvincing resemblance to true lapis. Such artificially produced stones are sometimes sold as "_Swiss lapis_." They are harder than true lapis and probably wear much better in exposed ornaments, but they are not lapis and are never of equal color, and names should not be misused, and especially is this true in a trade where the public has had to rely so completely upon the knowledge and the integrity of the dealer. With the increase of knowledge about precious stones that is slowly but steadily growing among the public, it becomes more than ever necessary for the jeweler and gem dealer to know and to use the correct names for all precious stones. The student who wishes to learn more about the matter will have to cull his information from many different works on gems. G. F. Herbert-Smith, in his _Gem-Stones_, gives a three and one half page chapter on "Nomenclature of Precious Stones" (Chap. XIII., pp. 109-112). The present lesson has attempted to bring together in one place material from many sources, together with some suggestions from the author. LESSON XXI WHERE PRECIOUS STONES ARE FOUND