210 A. R. Andrew—The Doilgelley Gold-belt. 
as the Clogau and St. David’s lode, runs up over the shoulder of the 
Clogau Hill and down the other side to the Afon Cwm-Mynach. 
Near the top of the hill it is cut across by the north and south 
Bryntirion fault, which moves the eastern end 100 yards to the north. 
This eastern end has been known as the St. David’s lode, the western 
end as the Clogau. After it passes over the Clogau Hill the lode 
becomes thinner and poorer, and little work has been done on it. 
The lode continues, however, as the Cae-mab-seifion lode. On the 
slopes of Clogau the lode has been worked for a distance of about 
1 mile; the combined outcrops of the continuous Vigra, Clogau, 
St. David’s, and Cae-mab-seifion lodes may be traced for about 34 miles, 
the longest known line of outcrop in the Dolgelley Gold-belt. 
The strike of the Clogau lode is 35° east of north, the dip being 
vertical with slight oscillations to either side. For a great distance 
the lode lies among the Clogau black slates,to which it runs parallel 
in strike though not in dip; throughout its whole length in the 
Clogau Beds it is intimately associated with the Llech-fraith green- 
stone sill. The walls of the lode very often show slickensides, and 
are in most places separated from the vein-stuff by more or less 
distinct clayey selvages. To the north-east the lode leaves the 
Clogau Beds and traverses the Gamlan Shales, where it is associated 
with very few greenstones. 
The lode, or rather lode system, branches into parallel veins connected 
by cross-veins and stringers; thus there are three lodes in the St. Dayid’s 
Mine—the north, the main, and the south; to the south-west they 
unite to form one lode with frequent stringers and offshoots. These 
individual lodes vary greatly in width, ranging from 20 feet down to 
streaks, inches only in thickness. 
Fragments of the wall rock frequently appear in the vein-stuff of 
the lodes, and these black, often taleose fragments of shale may at 
times give a brecciated appearance to the vein. The vein often has 
a banded structure, due to stringers or bands of slate or greenstone, 
separated from each other by bands of white quartz; drusy cavities 
are common. In addition to the white quartz and calcite which 
carries little besides pyrites and pyrrhotite, there is also a dark 
quartz, discoloured by inclusions of minerals and particles of the 
country rock. Pyrites, pyrrhotite, chalcopyrite, galena, blende, arseno- 
pyrite, tetradymite, and gold occur, chiefly in the darker quartz; of 
these, gold and chalcopyrite are the only ones that occur in abundance. 
During the years of which full returns have been published 
(1861-1907), these lodes have returned 77,501 ounces of gold from 
145,080 tons of quartz. Analyses of gold from the Clogau lodes gave 
the following results (27) :— 
Gold. Silver. Quartz. Tron. Copper. Loss. Total. S.G. 
(1):90°16. ..) 9°26... °B2 4. tiace. .. ‘trace. |. +26), 10000 RR aliaee 
(2) 089283 ys 924s aco eace —... 19. |:, ,100:00 ae lore? 
The gold is very variable in its distribution, the rich patches being 
found in a most unevenly scattered system of pockets. Some of the 
pockets are very rich; in one case 130 ounces of mixed quartz and 
gold, broken from the lode, were melted down direct, giving 116 ounces 
of retorted gold. The pockets are, as a rule, found in the bands of 
