Gems Notes and Extracts Augusto Castellani, Mrs. John Brogden 1871

234 GEMS.EPILOGUE.AFTER having carefully considered the differentgems,and with as much minuteness as I have found possible,it seems to me that it will be useful to collect underthe classes, genera and species to which they belong allthe substances mentioned in our catalogue, the greaterpart of which are called precious stones.Let us remember, then, that all the mineral constituentsof our globe are divided into three greatclasses, viz. :1. Minerals combustible.2. Minerals metallic, or metals.3. Minerals lithoid, or stones.Amongst gems, the diamond belongsto the firstclass, that is, the combustibles, and must be considereda variety of carbon properly so called, underthe genus of carbonates. With this are comprehendedthe carbon, or opaque black diamond, and theboort, or knotted diamond.Of the second class, that is, of metals,it does notfall within my province to speak, because, althoughgold, silver, platina, and other similar metals, arecommonly used ornamentally, and aie called preciousmetals, we have excluded them from our treatise,because they must not in any degree be identifiedwith gems, and neither could we .speak of them with-