234 HISTORY OF CALIFORNIA. 



however, if the surface is dull, the true color and appear- 

 ance are easily restored by rubbing, and when polished 

 it takes a very vivid lustre, which is preserved for a 

 long time in the atmosphere. 



Although in the division which has been intro- 

 duced into gold-yellow, brass-yellow, and grayish- 

 yellow, native gold seems with some slight modifica- 

 tions to agree with the geological relations of its 

 varieties, yet this mode of arrangement deserves little 

 serious notice. The gold-yellow varieties comprise 

 the specimens of the highest gold-yellow colors, though 

 there are some among them which have rather a pale 

 color ; they include most of the crystals and of the 

 imitative shapes, in fact the greater part of the species 

 itself. The brass-yellow native gold is confined to 

 some of the regular and imitative shapes of a pale 

 color (which is generally called brass-yellow,) and, as 

 it is said, of a less specific gravity than the preceding 

 one ; but this docs not seem to have ever been ascer- 

 tained by direct experiment. The grayish-yellow 

 native gold occurs only in those small flat grains which 

 are mixed with the native platina, and possess a yellow 

 color a little inclining to gray ; they are said to have 

 the greatest specific gravity of them all. The real 

 foundation of this distribution seems to be the opinion 

 that the first are the purest, the second mixed with a 

 little silver, and the third with platina. It is n^t 

 known whether the latter admixture really takes place, 

 but it is certain that several varieties of gold-yellow 

 native gold contain an admixture of silver.* 



In color and lustre, inexperienced persons might 

 mistake various substances for gold ; these are chiefly 



♦ Mobs' Mineralogy, by Ilaidinger, vol. ii. p. 438. 



