60 



BUXSEN OX THE FORMATION OF 



If the formation of palagonite really takes place in the way 

 pointed out, it must be possible to obtain this mineral artificially 

 by similar means. And, in fact, this m^ay easily be done by 

 igniting an intimate mixture of 1 part finely-powdered basalt 

 and 13 parts of slaked lime and elutriating the mass thus ob- 

 tained with water. The product consists of a mixture of lime 

 and palagonite, which may be recognized under the microscope 

 by its peculiar characteristics. Nevertheless we are obliged to 

 infer that the greater number of palagonites, and especially those 

 of Iceland, have not originated from such a reaction of pyroxenic 

 rocks and limestone, from the fact that carbonate of lime scarcely 

 ever occurs as a constituent of the undecomposed palagonites of 

 Iceland, and also because the per-centage of lime in the mineral 

 itself, calculated for anhydrous substance, does not equal the 

 per-centage of the same constituent in the normal pyroxenic 

 rocks ; for which reason it is not well possible to imagine that 

 palagonite, poor in lime, can originate from pyroxenic rocks 

 rich in lime, in consequence of a further addition of this con- 

 stituent. On the contrary, it might be expected that alkalies 

 would give rise to the formation of palagonite more readily than 

 alkaline earths, as they do not necessarily require to alter the 

 proportion of the constituents in palagonitic pyroxenic rocks. 

 Experiment fully justifies this conjecture. The most beautiful 

 palagonite powder, possessing all the mineralogical and chemical 

 characters of the Icelandic, is obtained when finely-powdered 



* After deducting the oxygen belonging to the ])hosphates and carbonates. 



