There is, as every schoolboy knows in this scientific age, a very close chemical relation between coal and diamonds. It is the reason, I believe, why some people allude to coal as “black diamonds.” Both these commodities represent wealth; but coal is a much less portable form of property. There is, from that point of view, a deplorable lack of concentration in coal. Now, if a coal-mine could be put into one’s waistcoat pocket–but it can’t! At the same time, there is a fascination in coal, the supreme commodity of the age in which we are camped like bewildered travelers in a garish, unrestful hotel. And I suppose those two considerations, the practical and the mystical, prevented Heyst – Axel Heyst – from going away.
Joseph Conrad, Victory, 1915. page 1.