durainn.

1919 M. C. Stopes in Proc. Royal Soc. B. 90 472 These four distinguishable ingredients, all of which..are to be found in most ordinary bituminous coals, I name provisionally as follows:—(i) Fusain. (ii) Durain. (iii) Clarain. (iv) Vitrain. Together the equivalent of ‘bright’ or glance coal of various authors.

1930 Engineering 18 July 92/1 Vitrain and durain belonged to the former [coking coal] and fusain to the latter [non-coking coal] class.

1950 P. J. Wilson & J. H. Wells Coal, Coke, & Coal Chemicals iii. 59 Exact correlation of the Bureau of Mines and the British terminologies, particularly the clarain and the durain of the latter, is not possible on account of the different bases for the classification.

1961 W. Francis Coal (ed. 2) vi. 312 Generally American coals appear to contain much less durain than British coals.