The real test for gem dealers comes next month in Las VegasThe U.S. colored stone market continues to move in a positive direction. Dealers are reporting good demand from retail jewelers for stock. This trend was evident at the Tucson gem shows and reportedly has continued to improve into the spring.Western buyers attending the Hong Kong International Jewellery show in March found the fair to be busy in spite of strong asking prices. Better-to-fine quality sapphires remain in high demand with tight supply. Likewise, shortages of fine ruby continue to put pressure on prices in all markets. (Hong Kong is the primary market for ruby: Jewellery News Asia recently reported that more than 50 percent of ruby processed in Thailand is exported to Hong Kong, while just 8 percent is exported to the United States.)Prices for ruby have been bifurcated; the quality of polished material is either very