The English colonist in the New World imported white indentured workers at first, but found there weren't enough of them. The Indians in the Americas refused to work or proved to be poorly fitted for long hours of hard labor. The Europeans found it easier and cheaper to import Africans as slaves. By the seventeenth century, the African slave trade was booming in the Americas. The slave dealers made so much money from their human cargoes that soon Africans came to be known as "black gold".
http://www.economist.com/node/21556890 http://wiki.answers.com/Q/Slaves_were_called_black_gold._why... http://www.unesco.org/bpi/eng/unescopress/2001/01-91e.shtml http://www.discoveryeducation.com/teachers/free-lesson-plans... ...
> I have been able to find a few references to "black gold" meaning slaves
I am not claiming that no one has ever used the term to mean slaves.
What I am disputing is (1) your claim that in the 19th and 20th centuries the term was popular with this main meaning, and (2) your claim that it had anything to do with Islam.
On #1, I find that the term was extremely rare until it started being used to describe oil in the 20th century.
On #2, note that the slavers mentioned in your particular links were all Western European or American. Guess how many of them were Muslims? I'm thinking the answer is somewhere between "exactly zero" and "zero to within statistical sampling error".
Most kidnapped slaves never did end up in the western slave trade by the way, but were instead kidnapped into north africa and the middle east (which was the effective center of the muslim empire, they even relocated mecca into africa). Almost none of them survived, and today with a few small exceptions no significant numbers of those slaves survive.
I am not an expert on the slave trade, but my understanding is that most of the slaves in the western slave trade were bought in West Africa, which was never part of the Ottoman Empire.
(I'm not saying that the Ottoman Empire was never involved in the slave trade. It was. So was the British Empire.)
> they even relocated mecca into africa
????
I just did a Google book search for "black gold" on 19th-century books, and checked the first 100 results. None of them had anything to do with slavery (or with mineral oil). So far as the Google n-gram tool's corpus knows, the term became popular around 1920-1940.
I have been able to find a few references to "black gold" meaning slaves, but so far as I can tell from the snippets available on the web they have nothing to do with Islam. In the few cases where I can tell who the slavers were, they were specifically Americans.