124

pressed and folded irregular layers of hard, brilliant coal, alter-
nating with layers whose appearance varies. Some of these are
wholly dense black, lustreless material, in sharp contrast with
the bright variety. These dead black layers have a gradational
relationship into the brilliant coal, and it is in these intermediate
bands that the peculiar texture is seen. The intermediate layers
consist of spherical grains of dull black material embedded in a
matrix of the brilliant coal. The spherical bodies average about
2 mm. in diameter, and are occasionally rod-like in shape. The
relative amounts of these bodies and of the matrix of brilliant
coal vary; the spheres are usually closely packed together, and
grade on the one hand into dense layers of dull coal penetrated
at the margins by films of bright coal; and on the other, rather
sharply, into the layers of brilliant coal.

In order to determine if possible any structure that the
spheroids might possess, highly polished fragments of the coal
were examined with the aid of a metallographic microscope used
for examining opaque substances by reflected light. No particu-
lar structure was visible even with the highest magnifications.
The dull spheroids were seen to contain minute irregular specks
of bright coal embedded in the dull material. In various portions
of the surface examined, the bright patches increased in amount,
and formed ramifying veinlets, marking off the surface of the coal
into circles of dull material and intercircular areas of bright coal
(Plate XVI B).

The composition of the brilliant coal is given in analysis 11 on
page 125 and, as already stated, it is that of a rather pure anthra-
cite. The composition of the duller bands and dull spheroids,
as shown by blow-pipe and qualitative tests, is that of clay iron-
stone or ferrous carbonate mixed with carbonaceous matter.

The iron carbonate probably was formed by the iron of the
ferruginous solutions from the surrounding basic igneous rocks
being precipitated as ferrous carbonate by the carbonaceous
matter of the coal seams, then in process of accumulation. On
account of the abundance of carbon, siderite, and not limonite
or bog iron ore, formed.

The peculiar texture is regarded as being of inorganic and
also of secondary origin. It is supposed that while such chemi-