LAS VEGAS–(BUSINESS WIRE)–The diamond market was relatively quiet in September as various Jewish and Indian festivals disrupted activity. Dealers remained optimistic for the US holiday season after positive trading at the Las Vegas shows in late August. China’s economic slowdown brought some caution into the market. Polished prices softened for goods below 1 carat but firmed for diamonds above 1.50 carats. The RapNet Diamond Index (RAPI™) for 1-carat diamonds slid 0.5% during September. RapNe