Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/146

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If we now compare the analyses of these different rocks in order to ascertain, if in their chemical composition, there is the same analogy which their geological situations seem to indicate, the result of that examination will prove by no means so conclusive.

Although serpentine is in itself a simple rock, we find it so often mixed with foreign substances, that it is impossible to obtain by chemical analysis any uniform results. Thus Kirwan has found in one experiment, 0,18 of alumina, while Klaproth found none. Kirwan gives 0,28 as the proportion of magnesia, Bayen 0,33: but there are even greater differences in these analyses.

With regard to the analyses we have of diallage, by Vauquelin, Drappier, Heyer and Gmelin, they all state a greater or less proportion of lime, a substance never found in serpentine. The smaragdite contains besides, according to Vauquelin, as much as 0,08 of oxide of chromium, and a little oxide of copper. There are also great differences in the proportions of the same principles in the green and metalloidal varieties. Vauquelin found in the first, 0,06 of magnesia, 0,21 of alumina; and Drappier found in the second, 0,29 of magnesia, and only, 0,03 of alumina. Lime is also, according to Hœpfner and Theodore de Saussure, one of the component parts of jade, but the first finds in it as much as 0,38 of magnesia, while Saussure makes no mention of it. On the other hand, Saussure found soda and potash in jade, but Hœpfner does not seem even to have suspected their existence.