Diamond prices opened a touch lower from last week’s year high in quiet trading volumes.%%The main PolishedPrices index, which tracks all sizes between 0.3 carats and 3 carats, opened 0.9% lower at 128.4 points. This is 3.9% above its level of this time last year and 2.4% higher on the year so far.%%Most Commercial and Mixed qualities were in negative territory. However, Fine one carat diamonds continued to strengthen, gaining 4.5% on the week.%%The definitions of groupings are:%%Fine: goods better than I colour and VS2 and above.$$Commercial: K SI3 and above, excluding the Fine category,and$$Mixed: the rest down to M I3