181 KEH.MOU : CEOr.OCY AND COAL RESOURCES OF KOREA, C. P. 
from horizon 1, GorLjhcIa Nala, showed a specific ffravity of 1"52, 
and had the lamina) so fine as to look at first sight like 
entirely bright coal (see table 1 for analysis). 
The dull coal can only be so called by comparison with the 
bright coal. It really has a distinct lustre varying from greasy 
to silky, and often shows as low a specific gravity as bright coal. 
Thus a dull greasy-looking shaly coal from Kaclihan Kundi Nala 
has a specific gravity as low as 1-36. As will be seen from the 
analysis in table 1, such coal is of high quality. Specimens of 
banded bright and dull coal from seams 1 and 2, Karar Khoh 
(Kaoria Nala), show G=1'35 and 1-38 respectively. 
The dull coal tends to possess a shaly structure, and seems to 
gradate (see analysis of K. 3, table 1, for an intermediate stage) 
into a stony coal-shale or shale-coal of very distinctive appearance. 
This is heavy (G=:1'64:), with a grey-black colour, almost 
bluish in the sun, a greasy lustre and a conchoidal fracture ; 
the general appearance is that shown by some varieties of 
psilomelane, except for the fact that this shale-coal is commonly 
thickly besprinkled with fragments of carbonised vegetable matter, 
and that it often shows small stringers and veinlets of bright 
coal. It tends to fracture into slabby pieces, but the shaly 
structure is not well developed. I refer to it, however, as shale- 
coal in this report. Its composition is well shown by the analysis 
of D. 154 in table 1. 
In addition, any of the varieties of coal may show films of 
' mineral charcoal ' or ' mother-of-coal.' 
The coal seams are composed of these varieties of coal in differ- 
ent proportions at different localities. Moreover there seems to 
be every gradation from the dull oal into carbonaceous shale, so that 
where the partings between coal seams are of a highly carbonace- 
ous nature, it becomes a matter of personal preference whether the 
two seams should be grouped as one or kept separate. My tend- 
ency has been to separate them, but I have followed no rule in 
this matter, except that of convenience. 
The results of the assay of samples of Korean coal taken by 
me are scattered through the following pages. 
00.5°"^°"'*'°" instructive to give here a summary 
of results for purposes of comparison. For this 
purpose the mean composition of each group of samples seems the 
most suitable : — 
