As the JCK Show in Las Vegas opens today, sentiment in the markets is improving, reports Diamonds.net. There are stable prices for some types of diamonds, underpinned by shortages. However, there is still a large supply of poor makes. Demand in the United States is solid but far from spectacular as jewelry chains' reports this week showed. The biggest development of the week: the decision by the world's biggest miners to create the Diamond Producers Association with a $6 million budget for diamond promotion.