A. R. Andrew—The Dolgelley Gold-belt. 265 
Glasdir Lode.—This lode has been worked extensively for copper, 
and like so many of the other copper veins of the district, it has been 
found to contain gold in addition. The lode is situated on the hills 
on the eastern bank of the Mawddach below its confluence with the 
Afon-wen. The lode is confined to the lower part of the Ffestiniog 
Flags, and its extension in strike is apparently hmited. At the main 
workings the lode courses in a north-east direction, but its whole 
observed length of outcrop is not more than 100 yards. At the west 
end the lode appears to pinch quite out, and at this point a thin 
quartz-vein, running north and south, cuts across it; this vein has 
been worked a little, but is very barren. West of the quartz-vein, 
and running parallel to it, a large wide cross-course or fracture cuts 
the line of the main lode, and has smashed up the rocks for quite 
80 yards; to the west of this, the main lode is lost. 
The main lode is usually vertical, and its dip, though variable, 
is always great. It differs from all the other veins of the country in 
the almost entire absence of quartz. A good section is seen where 
the main cross-cut is driven to intersect the lode. Looking north- 
east, we see—(1) on the right, a fault-plane about 1 foot wide in 
which the country rock is much broken up and comminuted to pug 
and clay; (2) about 20 feet of green flags and shales, bent about, 
distorted, and slickensided. These flags and shales are impregnated 
with chalcopyrite to such an extent that they have been mined for 
some years for copper; the average tenor of the lode at this level is 
about 1 per cent. of copper, while in the deeper levels it rises and is 
said to approach 2 per cent. Blebs of quartz, usually white and 
poorly mineralized, occur throughout the impregnated flags, but they 
have no definite arrangement. In places the width of the impregnated 
zone or lode is as much as 50 feet; it has been opened up consider- 
ably in depth, but very little work has been done along the strike. 
The deposit has been formed by cupriferous solutions, rising through 
the fissure on the south-east side of the lode, passing thence into the 
flags, and there depositing part of their copper contents. It will be 
remembered that the flags are bent and crushed about, so that they 
readily allow the passage of mineral solutions, and the diminution of 
pressure in them would probably facilitate the deposition of the 
minerals held in solution. The almost total absence of quartz is the 
unique feature of this lode. Besides chalcopyrite, the only metallic 
minerals I noticed in the lode were pyrites, bornite, and erubescite. 
In 1900 this lode produced 1993 ounces of gold. The copper con- 
centrates generally assay about 1 ounce of gold to the ton. 
Ffridd-goch Lode.—High up on the eastern bank of the Afon-wen, 
more than a mile above its confluence with the Mawddach, the Ffridd- 
goch lode strikes 5° east of north, and dips steeply (70°) to the 
eastward. It can be traced for about 1200 yards; it is confined 
throughout to the lower parts of the Ffestiniog Flags. At its southern 
end the lode runs along and through several greenstone sills, but 
further north the latter die out. At places the lode is accompanied 
by one or more parallel lodes. Where it has been opened up it is 
well defined, and commonly 3 feet in width. The quartz is poorly 
mineralized, pyrites is the most usual metallic mineral, a little 
