Thin Shale Research Articles

On the Composition of the Coal Balls and Baum Pots in the Lower Coal Measures

In the Halifax Hard Bed Coal seam it is well-known that nodules occur in abundance; these nodules are locally known as “ coal balls.” Just above the coal is a bed of shale in which nodules called “ baura pots “ are found; the latter is divided from the coal by a thin shale containing Aviculopectens in abundance; under the coal is a hard fire-clay called ganister. “Coal balls” are generally spherical, of a brown or greyish-brown colour internally, they are very hard and contain the remains of plants, in some instances being largely composed of wood fossilized by carbonate of lime; they have generally a coating of iron pyrites, which occasionally replaces the carbonate of lime and becomes the chief constituent of the ball. “ Baum pots” may be divided into two kinds—first, those consisting of successive coatings of mineral matter surrounding a central portion; second, those showing stratification like the shale in which they occur. “Baum pots” are generally oval, of a grey colour, hard and compact and often contain fossil shells. They have frequently an outer coating of iron pyrites. I am not aware that the composition of these nodules has been examined in detail, it being generally stated that they are composed of limestone coated with, iron pyrites. With a view to learn something more as to their composition I have made analyses of two “coal balls” and one “baum pot” from the Halifax district. On examination of the “coal balls” qualitatively I found the ...

On some less common Bathgate fossils

The limestone of the Bathgate Hills abounds with fossils, and these are for the most part in a remarkably fine state of preservation. When wholly enclosed in the limestone, they always retain their perfect form, that is, if they have been embedded entire, though their external markings are not always to be seen. These markings are there, but the fine coral or other debris that had filled up the shell in many cases separates more readily from that shell than the shell does from the matrix in which it is enclosed; hence we have what are called casts of fossils. From the cast it is often difficult to determine the species; by a little careful chipping, however, one sometimes succeeds in getting a fragment showing the external markings. When the fossils lie at the top of any of the divisions of the limestone, and have been only in part embedded in it, they are seldom entire, at times distorted besides, especially the larger ones. Those that occur in the thin shale partings between the massive layers of limestone are almost always flattened and imperfect. In many parts in the west of Scotland, Mr Young, in his work on that district, states that it is mainly in the shales that the fossils are to be found, and few in the pure limestones. In the Bathgate Hill, on the other hand, the fossils are most numerous and finest in the limestone. A few miles to the south, however, where the limestone becomes