A, R. Andrew—The Dolgelley Gold-belt. 209 
the west. The lode ranges up to 6 feet in width, averaging about 
13 feet throughout its traceable length. The quartz is poorly 
mineralized, containing occasional pyrites only. The lode occurs 
in the Gamlan Shales, and runs along and across numerous greenstone 
intrusions; it occupies a fault plane which can be traced for several 
miles north and south. 
West Vigra or Nant-goch Lode.—On the west side of the Vigra 
Mountain there are several abandoned copper workings close to the 
Nant-goch Farm. The lode worked can be traced for about 13 miles 
over the shoulder of Y Vigra to the Hirgwm stream, and perhaps for 
half a mile beyond, its strike being 35° east of north. The part on the 
west flanks of Y Vigra used to be called the Nant-goch lode; that on 
the north flanks the West Vigra lode. The lode is vertical; in width 
it varies from a few inches up to 20 feet. Besides quartz the lode 
contains abundant chalcopyrite, pyrites, and pyrrhotite, with a little 
galena ; the latter becomes the most common mineral where the lode 
erosses the shoulder of the Vigra spur. Assays of this lode in 1861 by 
Readwin (34) gave 13 grains of gold per ton. In the south the lode 
traverses the Pen Rhos Slates; towards the north it traverses the 
Vigra and Clogau Beds, and finally dies out in the Gamlan Shales. 
The lode as a rule runs along the junction of the sedimentary rocks 
and the many greenstone intrusions which occur along its course. 
Vigra Lodes—The Vigra Mine worked on two intersecting quartz 
lodes, which formed a conspicuous outcrop of white quartz high on 
the flanks of Y Vigra. One of the lodes strikes almost due east and 
west, dipping to the south at an angle of 70°. It can be traced for 
a distance of 300 yards only to the west of the workings, and here it 
has been worked to some considerable extent. In width it varies 
from 4 to 6 feet; the lode material is of clear white quartz, carrying 
in places chalcopyrite. The second of the lodes is more important ; 
at the Vigra Mine its strike is 60° east of north, dipping 75° to the 
north; to the west it can be traced for a distance of 1000 yards; to 
the east it can be traced into the continuation of the St. David’s lode. 
At the Vigra workings this principal lode system consists of two 
parallel veins about 30 yards apart, connected with each other by 
a series of leaders and cross-veins. Both these veins are irregular in 
width, swelling out to 6 feet and then pinching in to a few inches. 
A low-level cross-cut was driven to intersect the lode at a depth of 
about 400 feet below the upper workings, but was not successful in 
picking up the lode at that depth. The lode matter is quartz 
impregnated with copper pyrites; enclosed in the lode are blocks of 
black shale impregnated with chalcopyrite, bornite, erubescite, arseno- 
pyrite, and to a small extent gold; in some parts the lode contains 
rhodonite ; the mine waters are acid and carry copper in solution. 
At the Vigra workings where the lode is best developed, it crosses the 
Vigra Beds of the Maentwrog; to the west it crosses the Pen Rhos 
Beds, while to the east it enters the Clogau Beds. Where the lode is 
most prominent it is accompanied by intrusive greenstones. 
Clogau_ and St. David’s Lode.—This and the Gwyn-fynydd lode, 
which will be mentioned later, are the principal lodes of the Dolgelley 
Gold-belt. The easterly continuation of the main Vigra lode, known 
DECADE V.—VOL. VII.—NO. v. 14 
