My first attempt at posting this seems to have gone directly to Roger
Gosling - so I'll try again.
According to Iain Williamson ("Coal Mining Geology" p.63) coal balls vary in
size from 2 inches to 2 feet in diameter, often circular or elliptical but
sometimes irregular in shape. Many are found to contain excellent evidence
of plant structures completely petrified by secondary carbonate materials
and clearly show the delicate tissues of bog flora of the carboniferous
period.
During her time as a paleobotanist, Marie Stopes (yes, the 'Married Love'
one) studied coal balls in the Burnley area where they are fairly commonly
associated with the Upper Foot and Lower Mountain Mines. Roger mentioned
the Todmorden Moor collieries which were on the eastern edge of the Burnley
coalfield and worked the above seams, which had united to form the Union
Mine. Stopes also looked for, but did not find them in the Brora coalfield
of Caithness.
Best wishes,
Mike Gill
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