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

INTRODUCTION.Chemical discoveries very much assisted the rightclassification of minerals, introducing in the science anew law, founded on analysis, which helped to confirmor slightly modify that which had been already establishedas to crystalline forms. Berzeliiis, Weiss,Becquerell,Ebelmen, Brewster, Mitscherlich, Brocchi,Spada-Medici, Pouzi, and a number of learned men ofevery other nation contributed tothe science.the advancement ofNow, the learned, generally speaking, divide mineralsinto three classes : the first contains combustibleminerals; the second, metals; the third, lithoids orstones.These three classes are subdivided, as we havealready remarked, into genera, species, and varieties.To the first class belongs the genus of carbonates,which is divided into four species, the first of which iscarbon, properly so called, and of which one of thevarieties is the cubic carbon, otherwise the diamond.The third class distributes stones into twenty-fourdifferent genera, which are subdivided into many morespecies and varieties.refrain from giving theFor the sake of brevity we shalldenomination of each of thesetwenty-four genera, or orders, as they are called byothers.It is sufficient for us to know that amongst theseorders are the alumina, the silicates, and the fluorites.To the alumina belongs the species of corundum, ofwhich the ruby, the sapphire, and, in short, all socalledoriental gems are varieties. Amongst the silicatesis pure silex or quartz, from which is derived