And I'm sorry brother, the latest from the ulema is that zakat is to be payed on anything that has monetary value including currency and diamonds etc...
And think with open mind, doesn't it look unfair that someone keeps amassing huge amounts of diamonds and doesn't pay anything to the poor...
And if you are buying diamonds just to avoid paying zakat because it feels like a burden to you, then you are clearly doing wrong, because Allah judges you based on your intention..