Definition of niacin for English Language Learners. : a type of natural substance (called a vitamin) that is found in certain foods and that helps your body to be healthy.
Red diamonds are the most expensive in terms of money per carat, since red is the rarest colour of natural diamonds.
The Pink Panthers gang have been responsible for stealing an incredible 240m worth of diamonds. Here we look at some of the most expensive jewels in the world, and the dramatic stories attached to them. Great Star of Africa. At 530.4 carats, the Great Star of Africa is the largest polished white diamond in the world â and was cut from the 3,106 carat Cullinan, the largest diamond crystal ever found.