380 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



following the ancient customs of our old colonies. The foreman, 

 with a little hammer or pincers, without regard for geometrical 

 beauty, for which mineralogists have a sort of worship, applies him- 

 self to brealdng out tlie stone,^ an operation which consists in reduc- 

 ing the mass to small pieces, in order to detach the limpid portions 

 and to separate them not only from the rest of the veinstone, but 

 from all that which, in the material, is not usable, and it is inider this 

 rough form of angular debris that the gems are exported to Europe 

 for the final cutting. 



The alluvial deposits are very different from deposits "en place" 

 and less attractive. Minerals are no longer found in any sort of 

 collective relation in their mother rock. Under the influence of the 

 phenomena of alteration during centuries, they have been detached 

 from their gangue little by little, drawn away from the place of their 

 origm by the superficial trickling down, and hurried along much more 

 quicldy as they are less dense until they have been carried a long 

 distance by torrents and mixed with other species of different nature 

 and origin. 



Under the tumultuous waters which consume the most resistant 

 mountains, pursuing without truce a sort of eternal struggle for life, 

 the weak minerals, the soft and fragile ones, are worn away, crushed by 

 the strong, I should say by the hard minerals, and are eliminated in 

 the form of fine clay ; the strong resist much longer, but whatever they 

 are, their crystals sooner or later lose the brilliancy of their faces, the 

 keenness of their edges, and before disappearmg in their turn they 

 are reduced to the condition of round pebbles. Among them, of 

 equal hardness, those are preserved the longest that are devoid of 

 physical blemishes. This is a gigantic mechanical prej^aration, a 

 formidable cutting, eft'ected by natural action. It is a selection 

 through force and beauty. 



Further, the gems that subsist in beds, where they are often asso- 

 ciated with heavy and precious mmerals, such as gold, pertain to a 

 number of more limited species; though as a rule they are less abun- 

 dant, yet the proportion of beautiful stones in such cases is generally 

 great. At Madagascar these stones are chiefly corundums, garnets,^ 

 occasionally some chrysoberyl, some spinel, and topaz. 



One of the most typical of the alluvial deposits among those I 

 visited is found to the southwest of Ambositra, in the bed of the 

 small river Ifempina. Its boundary is not at all a wilderness of 

 weeds like the Sahatany, but a forest in all its splendor, impenetrable 



' In certain works the cutting is not done in the camp (toby), but at the prospector's headquarters (Ant 

 sirab6 for example). 



- The most frequent is almandine, wliich sliows a wide range of color from dark red to a pretty rose. Many 

 of the cut almandines come from Pluvious. 



