Prices for rough diamonds are on the increase. One of the largest diamond companies has reported that rough diamond prices have recently risen as much as 8.5%. The increase in rough diamond prices is expected to cause an increase in polished diamonds. This increase is likely to be somewhere in the 4% to 5% range. According to an expert the price increase is going to effect mainly diamonds that are of high quality.While the prices may increase the demand for large and high-quality diamonds is thought to continue to increase.