Wealth for some...
It is of course an enormous oversimplification to suggest that the mere presence in a country of significant mineral resources implies that it will be misgoverned. Perhaps it would be more accurate to observe that, during the industrial period in which those resources have been of particular use to competing economies, the leading technological powers of Europe and, later, the United States have built extended colonial empires and appropriated the buried riches of each country in which they found them.
Coal is only one of the resources that imperialism can change from blessing to curse.
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Thus, to the extent that concentration of resources correlates with social injustice, it may be said to be principally a consequence of colonialism, which uniformly produces unrepresentative, kleptocratic puppet regimes in which a small ruling elite sells national resources to colonial powers and pockets most of the proceeds.