Polished diamond prices continued to rise in June, according to Rapaport Research.
In a release, the company noted that "while some price resistance is apparent, the outlook for the second half of the year remains strong."
It added that rough prices are continuing to rise, estimating they have jumped 30 percent to 35 percent in the first half of the year.
"The first half of 2011 proved to be a positive period for the diamond industry, but dealers are concerned that the pace of growth might not be sustainable as rough prices may be overheating," the company said in a statement.
The RapNet Diamond Index for 1 ct. diamonds rose by 7.4 percent in June to 109.17. It also rose 13 percent for 0.50 ct. stones, and 8.2 percent for three caraters.
The overall RapNet Composite Index increased by 8.4 percent to 179.96 during the month.
Additional information about the state of the diamond market is available in the Rapaport Research Report, “Half Way There,” at diamonds.net/report.