DeBeers founded by British colonizer Cecil Rhodes

In the 1870s, during the period called the “scramble for Africa,” the
brutal Cecil Rhodes was colonizing Southern Africa, setting up the
African front of British imperialism. 
One of Rhodes’ primary endeavors was the large diamond mine in
Kimberley, South Africa. The gems from this mine made Rhodes a
multi-millionaire and consolidated his power in the region. The price to
African people was mass slaughter of tens of thousands and the
seizure of their territories. Whole populations were dispersed when
Rhodes dynamited them off their lands. African families were
destroyed as African men were rounded up by the thousands in forced
labor concentration camps near the diamond mines, a practice that
continues today.
The British colonial exploits in Africa and around the world followed on
the heels of more than three centuries of the trade in African people
themselves. The immeasurable wealth generated by the slave trade
catapulted England out of the poverty and ignorance of feudalism and
transformed it into a wealthy industrialized nation. It was this process
that brought about the birth of the capitalist system itself.
In his book
Capital
, written in the 1860s, Karl Marx raised the
question, how did capitalism actually begin? Where did it get its start
up money? He surmised that the capitalist system must have had a
first or “primitive” accumulation of wealth or capital coming from
outside of Europe—which was barren, impoverished and unproductive. 
Marx observed: “The discovery of gold and silver in America, the
extirpation, enslavement and entombment in mines of the aboriginal
population, the beginning of the conquest and looting of the East
Indies, the turning of Africa into a warren for the commercial hunting
of black skins signalized the rosy dawn of the era of capitalist
production. These idyllic proceedings are the chief momenta of
primitive accumulation.”
Omali Yeshitela, leader of the Uhuru Movement and Chairman of the
African People’s Socialist Party, pointed out more than a hundred years
later, however, that Marx’s statements about primitive accumulation of
capital were a “definition of the significance of the enslavement of
African people only as it impacted on development
inside
 Europe, a
development which necessarily means what has come to be called the
underdevelopmen
t of Africa, Asia and Latin America.”
This is true because if Marx really understood his own observation he
would have come to the conclusion that the force that could overturn
the capitalist system of workers and bosses would not be white
workers in Europe, but the Indigenous people entombed in the mines
and the Africans whose homeland had become a warren for the
hunting of black skins.
“Marx’s world was white,” Yeshitela asserts. “The enslaved Asian,
African and ‘Indian’ of North and South America were essentially
objects
 of history, having more or less significance for European
development.”
As white people we habitually ignore the unfathomable suffering
inflicted on African and other peoples that bring us the resources and
standard of living we take for granted. We happily deny the fact that
those resources, wrested at a price of hideous suffering to so many,
make up the foundation of the prosperity and opportunities of our
society.
The DeBeers diamond cartel has always done what the U.S.-backed
rebels of Sierra Leone, Liberia and Congo have done to African people,
and even worse. DeBeers simply had the power to hide it from the
view of the white world, for whom the fate of African people has never
been a concern in any case.
This is the context for the definition of “blood” or “conflict” diamonds.
It’s not just a particular atrocity that comes to our attention at any
given moment. It’s a centuries-long institutionalized process of ripping
the humanity, the beauty, the resources, land and independence out
of the soul of Africa for our benefit. 
Blood was dripping from diamonds long before the slaughter began in
West Africa in the 1990s.