ORES OF IRON 
135 
has yielded the highest grade hematite ores of the British 
Isles. They are gash-veins in the older rocks, and nodular 
masses and sheets in the Silurian and Carboniferous Lime- 
stones. The first group are of little economic importance. 
The Eskdale granite (granophyre), the Ennerdale syenite, 
and Skiddaw Slates are traversed by steep gash-veins of 
hematite which thin out as they are followed downwards; 
they have been worked in the granophyre to the depth of 
300 feet. The veins thicken where two of them intersect. 
Some cylindrical stems made of concentric layers and known 
as ‘ ring-ore ’’ were mistaken for fossil tree stems. The ore 
of the gash-veins was clearly formed by replacement of the 
ah. 
S 
) Gh. 
Sh. 
F16. 40.—Tur REPLACEMENT HEMATITE ORE-BODIES OF CUMBERLAND, 
R.S. and R.Sh., Permian red sandstones and shales; L., Carboniferous 
limestone; Sh,, shales; Sli, slate; F., fault, The ore-beds are 
shown in solid black. 
country rock by solutions descending along fissures, for the 
massive ore passes into iron-stained country rock, and the 
veins in the granophyre include unreplaced felspar. 
The most important of the Lake District ores are replace- 
ments in Carboniferous Limestone (Fig. 40), including large 
kidney-shaped masses of hematite (Fe,O3) which may con- 
tain 98 per cent. of iron oxide, with the phosphorus varying 
from ‘02 to +3 pér cent. The ore has replaced some thin 
beds of limestone, bosses of which remain on the floor of the 
seam. In some cases limestone has been partially replaced 
by infiltration from overlying sandstone and the ore forms 
funnel-shaped masses which may spread out below into an 
irregular sheet. The largest ore-bodies occur along faults,