The articles are long but fascinating. For example,

The illusion had to be created that diamonds were forever -- "forever" in the sense that they should never be resold.

. The other article starts from another angle - a thief trying to to steal money and launder it through diamonds:

In the fall of 1978, a thirty-two-year-old Californian computer wizard named Stanley Mark Rifkin discovered an ingenious way to become a multimillionaire overnight. While working as a consultant for the Security Pacific National bank in Los Angeles, he had learned the secret computer code that the bank used to transfer funds to other banks telegraphically at the end of each business day. With this information and his mastery of the bank's computer, he realized that he could transfer tens of millions of dollars to any bank account in America. The problem would be withdraw the money from the system. In early October, he devised a plan for siphoning this money out of the bank and converting it into Russian diamonds.

Luckily, my girlfriend doesn'tlike diamonds, which is cool with me, but now I'm having a tough time thinking of something else "really sparkly", which is what she's asked for. Tanzanite? I read on the internet (so it must be true) that it was controlled by terrorist organizations. Sapphires? Emeralds? Won't that look too much like costume jewelry. Maybe I should just go with cubic zirconia ...