Its a known fact that vested parties have interest in controlling the value of diamonds by controlling the influx of them.
Same can be said of any product being sold in a free market, depending on it's stage in the product life cycle.
I've worked in the industry for approx 15 yrs, so I can confirm that 99% of what I've read in this thread is bullshit and unfamiliarity with the diamond industry. The industry is very healthy (pre-2008 prices), there's a very noticeable difference in gem quality natural diamonds and synthetics, the Jews don't have a secret massive stockpile they're hiding in a bunker lol, etc etc.
Of course the gem industry is all about marketing, as is every other luxury good industry. Demand is forecasted to outstrip supply in the next 12-15 yrs as many old mines wind down. While the US consumption of approx 40% of gem quality remains fairly stagnant, the growth potential lies with the Chinese, who currently consume ~22% and steadily climbing. More than 10 million wedding a year and growing in China, and thanks to successful marketing diamonds are becoming a part of their culture as we'll. diamond industry is very healthy.
The Russian deposit will not have the enormous impact you think. There's plenty of very large known deposits on the planet. The vast majority are not feasible and won't be unless the price of stones skyrockets. Many factors to consider that are more critical than the size of a deposit.