GOLD. HI 



Obs. Native gold is mostly confined to quartz, intersect- 

 ing in veins, or interlaminated with, subcrystalline slaty or 

 schistose rocks, especially hydromica and chloritic slates. It 

 occurs sparingly in similar or other veins in granite, gneiss, 

 or mica slate. " It has also been found in traces, according 

 to J. J. Stevenson, in the trachytes of Colorado, and in 

 Silurian and Carboniferous quartzytes. 



The quartz intersects the slaty rocks in veins and lies in 

 thick seams between their layers. It is frequently cellular 

 for a considerable distance from the surface owing to the 

 alteration and removal of pyrite, galena, or other metallic 

 ores that may be accompaniments of the gold, and the 

 cavities are usually rusty with oxide of iron, and sometimes 

 contain particles of sulphur left by the decomposing pyrite, 

 and also strings or laminae of gold. The rock in this cav- 

 ernous state is rather easily quarried out ; but deep below, 

 where the minerals are not removed by decomposition, mining 

 is far more difficult. 



Pyrite itself is nearly as hard as quartz, when unaltered, 

 and readily strikes fire with a steel. This pyrite is often 

 very abundant, and contains throughout it considerable 

 gold ; but the gold is so finely distributed, that little of it 

 can be removed by the ordinary process of crushing and 

 amalgamation ; nature's Avay consists in decomposing the 

 pyrite and thereby making it drop its load. The galenite 

 of a gold region is also usually auriferous. 



Gold sometimes occurs in the slate rocks adjoining the 

 veins, though mostly confined to the latter. Auriferous 

 quartz often contains no gold visible to the naked eye. 



But while quartz veins are to a large extent the actual 

 repositories of the gold in its native state, a very large 

 part of the gold derived from auriferous regions has come 

 from the sand and gravel beds, in which it occurs in flat- 

 tened grains, and sometimes in lumps and nuggets. By dif- 

 ferent methods — erosion by running waters, movements of 

 glaciers, natural decomposition, and other disintegrating 

 action — the gold-bearing rocks have been extensively re- 

 duced to earth and stones, and this loose material has been 

 distributed along the river courses, making vast alluvial or 

 diluvial gravelly formations. From these gravels the gold 

 is obtained by simple washing, thus taking advantage of the 

 high specific gravity of gold. Streams are carried in aque- 

 ducts and thrown in great jets against the gravel bluffs to 



