(IDEX Online) - Polished diamond prices were down yet again during June, as the Index suffered its biggest monthly loss - 3.04 per cent - since the current decline began last March.That's significantly worse than last month, when the Index fell by 1.27 per cent. It was down 1.47 per cent in April and 0.98 per cent in March. The slide during June was marked by a steep decline in the middle of the month.Global demand remains weak amid ongoing geopolitical uncertainty. De Beers reported a year-on-year drop in rough sales of almost a third during the month, amid increasing sightholder caution.IDEX Online subscribers please click here to read the full report.