QUARTZ AND FLINT 163 



to suit his needs, shaped them into weapons, on which 

 he depended for his life, in defence against wild beasts or 

 in pursuit of prey for food, or as a means to yield him 

 fire. Great were their services ; untrumpeted by fame ; 

 belonging to a forgotten past. Now we find in them 

 material for investigation, and some of us take a curious 

 pleasure, to the astonishment of others, in following 

 their strange metamorphoses, searching out their history, 

 and weaving it into the general scheme we fabricate 

 of the world. 



NOTE ON THE CRYSTALLINE SILICA OF FLINT. 



The silica of flint approaches quartz so closely in most 

 of its properties that it is usually identified with this 

 mineral. Certain differences, however, exist, which are 

 worthy of consideration ; thus, for instance, the specific 

 gravity of quartz is 2'65, that of black flint only 2'59. 

 This might be accounted for by the presence of a certain 

 amount of opal. Thirteen per cent, of opal, with a 

 specific gravity of 2*2, would account for the discrepancy. 

 Water to the extent of 1 per cent, is not uncommon in 

 flint, and this would be sufficient to supply 16 per cent, 

 of opal. But again, quartz is far less readily soluble in 

 caustic alkalies than flint. Eammelsberg found that by 

 treatment with caustic potash 8 per cent, of quartz was 

 dissolved, and of flint 80 per cent., or ten times as much, 

 and his results have been confirmed by Henard and C. 

 Klement. * 



On the assumption that opal is present, this might be 

 accounted for in the folio wing way : the opal would first pass 



'' These investigators experimented on flint of sp. gr. 2'606, which 

 lost 1*3 per cent, on heating. Placed on the water bath in a 20 per 

 cent, solution of caustic potash, it lost 51 per cent, in three hours, and 

 86 per cent, in twelve hours. 



