Hey Mister, you have a good argument, however I beg to differ. I know Africa is responsible for almost 50% of the worlds diamonds, but it's mostly the Southern part of the continent (most of which doesn't even have any more volcanic activity) which is responsible for this. Countries such as South Africa and Zimbabwe have been shown to have the richest deposits of diamonds, but don't forget there are other deposits in India.

If Kilimanjro was still active, perhaps I would lean more towards the theory you support, but because like Longonot , this Mountain is extinct, I tend to "believe" that Jupiter could have something to do with it. After all, the gas giant isn't extinct yet.