gems, topaz

Early analysis of topaz. The analysis of this stone has already been carried out by Torbern Olof Bergman; but the results which he obtained being very different from mine, either as regards the number of the elements which constitute it, or their respective proportions, I believed it my duty to make my analysis public. The reason for this difference doubtless arises from the difference in the methods employed. The art of lithogeognosy has become so perfected during the past few years that there is reason to think that most of the analyses of sparkling stones formerly made do not provide a complete knowledge of their principles, and above all of the exact relation of these latter: we already have striking proofs of this for several stones examined by Bergmann, and among others for the oriental sapphire and the hyacinth, in which he found silica, alumina, lime, and iron, whereas Martin Heinrich Klaproth, who repeated this work, found only alumina in the first, and in the second a new earth united with a small quantity of silica.