Published online by Cambridge University Press: 14 March 2018
There occurs frequently in coal a white carbonate which, when it is referred to at all by scientific writers on coal, is usually described as calcium carbonate. It occurs as a rule in the form of thin layers infilling the joint-cracks which lie normal to the bedding-planes, though at times it may be seen infilling other divisional planes which may cut across the bedding obliquely.
1 I am indebted to the various colliery proprietors for kindly sending specimens. For the Llanelly and Ashby specimens, I have to thank Mr. F. H. Butler and Mr. L. F. Wallis respectively.