29 



is then, and tlien only, liberated from its connection there- 

 with. In these instances the quartz presents a porous or 

 " honeycombed " appearance, and so rendered more easily 

 workable. When gold is found in hard compact quartz veins, 

 and is even quite visible thereon to the eye, as a rule these 

 reefs are not always of a very permanent character. 



In alluvial deposits the gold is also found associated with 

 various minerals that have evidently been derived from the 

 same mineral vein — such as platinum, magnetic iron, chrome 

 iron, and tin oxide, as well as quartz, zircon, topaz, and even 

 the diamond. 



Miners, as a general rule, restrict their search to the one 

 metal — gold, discarding all others that may appear in their 

 " wash." So probably many valuable metals and precious 

 stones are lost that otherwise could be saved with profit. 



The occurrence of gold in quartz veins, and the presence of 

 the quartz veins themselves in plutonic and metamorphic 

 rocks, can be explained by chemical agency. The mineral 

 veins must have been deposited during a very disturbed 

 period ; but subsequently to the intrusive action of the 

 plutonic rocks, and the metamorphosis of the argillaceous 

 strata contiguous thereto. Intense heat must have prevailed, 

 while the semi-liquid fused masses uplifted, tilted up and 

 transmuted the Silurian formations, forming dykes by cutting 

 through them. During the contractions that must have 

 ensued on cooling, fissures would be formed both in 

 the intrusive dykes and the sedimentary rocks, which would 

 generally be across the direction of the cooling mass. These 

 fissures would then become filled with infiltrating hot solu- 

 tions of silica and minerals. Upon further cooling the silica 

 would be deposited and the minerals, including gold, would 

 likewise be precipitated, or gradually crystallise, and become 

 intermingled with the silica mass. 



The solutions of these minerals would be effected in this 

 way. During the prevalence of the intense heat that must 

 have been everywhere cotemporary with the igneous action of 

 the period, the temperature of all waters, vapours, and gases 

 would rise excessively high by reason of the enormous pres- 

 sure to which they would be subjected below at great depths. 

 All would be chaos : every substance would be subjected 

 to intense chemical agencies, and be continually undergoing 

 change. The hot waters and vapours would be dissolving what 

 was soluble, such as the alkalies, silica, and all the compounds 

 of the metals. These latter would be formed by gases and 

 acids of intense chemical activity that would be present, such 

 as chlorine, sulphuretted hydrogen, nitric and hydrochloric 

 acids. These would act and re-act upon all the minerals they 

 came into contact with, and the compounds thus formed 



