British Miner aloyy. 341 



sulphate of barytes*. These minerals as well as the native gold 

 itself are distributed very irregularly in the quartz of the lode. 



When the quartz contains patches of calcite, dolomite, and 

 chalybite, and includes splinters or fragments of the neighbour- 

 ing clay-slate, it is regarded by the miners as more promising 

 and likely to yield gold than when the lode consists of quartz 

 alone. 



Although the gold sometimes is found alone imbedded in the 

 colourless quartz, it occurs more often in conjunction with more 

 or less iron pyrites and the other above-mentioned metallic com- 

 pounds, which usually occur as small patches, nests, or aggrega- 

 tions in the quartz. 



When small pieces or splinters of the bluish-grey slate are found 

 isolated and enclosed in the quartz of the lode, it is common to 

 find the gold and other metallic minerals adherent to or crystal- 

 lized on the under surface of such fragments. This mode of 

 occurrence is very suggestive of crystallizationfrom solution, where 

 it is common to find the crystals developing themselves in prefer- 

 ence on the sides of any foreign bodies which might happen to 

 be floating about in the fluid — chips or straws for example. The 

 adhesion of the gold and- metallic minerals to the underside 

 of such chips or fragments of slate might be supposed to indi- 

 cate that the underside of such fragments had arrested the gold 

 &c. in the act of being carried into the lode-fissure from below 

 along with the stream of liquid quartz : this would be equally the 

 case whether the quartz is imagined to have been injected as an 

 aqueous solution, or in its known gelatinous state, or in a state 

 of igneous or hydro-igneous solution. 



The geological position of the Clogau quartz lode is in the Lower 

 Silurian Lingula-beds, close to their junction with the Cambrian 

 strata of the Geological Survey, on which these beds rest con- 

 formably ; and in close proximity to the lode they contain the 

 Paradoxides Davidis in abundance. 



In these strata are seen numerous intrusive masses, and, as it 

 were, sheets of true diabases (described and coloured by the 

 Geological Survey as greenstones), apparently at first sight con- 

 temporaneous with the beds themselves, but which, although fre- 

 quently found to follow the strike of the fossiliferous beds for long- 

 distances, and even at times to coincide more or less with their 

 clip, will nevertheless be sooner or later observed to break through 

 both the strike and dip of these strata and to be purely intrusive 

 rocks. 



* The above minerals were all found hy the author. Mr. Read win 

 stutes the following also to occur along with the Welsh gold: — bismuth, 

 bismuthine, grey copper, raispickel, orpiment, phosphate and arseniate of 

 lead, native lead (?), platinum (?), talc, oxide of iron, rutile. 



