EPILOGUE.
After having
carefully considered the different gems, and with as much minuteness as
I have found possible, it seems to me that it will be useful to collect
under the classes, genera and species to which they belong all the
substances mentioned in our catalogue, the greater part of which are
called precious stones.
Let us remember, then, that all the mineral constituents of our globe are divided into three great classes, viz. :
1. Minerals—combustible.
2. Minerals—metallic, or metals.
3. Minerals—lithoid, or stones.
Amongst
gems, the diamond belongs to the first class, that is, the
combustibles, and must be considered a variety of carbon properly so
called, under the genus of carbonates. With this are comprehended the
carbon, or opaque black diamond, and the boort, or knotted diamond.
Of
the second class, that is, of metals, it does not fall within my
province to speak, because, although gold, silver, platina, and other
similar metals, are commonly used ornamentally, and aje called precious
metals, we have excluded them from our treatise, because they must not
in any degree be identified with gems, and neither could we .speak of
them with-
