As the industry gears up for the all-important holiday season, conditions are mostly positive for the gem trade.Reports from the September Hong Kong Jewellery & Gem Fair indicate active demand for both diamond and colored stones. Gemstone buyers were not only hunting the classics but also a host of lesser-valued gems. Several ­dealers ­confirmed some price resistance in the heated corundum market, where prices have been rising in response to the strong prices realized for natural (unenhanced) ruby and sapphire.Emerald continues to be hot this fall. Current supply levels are good. Prices for the fine-quality Colombian material have increased again in recent months, and dealers are finally finding a more inviting market in China. Insufficient efforts to educate that market about the clarity enhancement of emeralds had buyers confused about this common practice. The market is also see