A.  The most sought after gemstones are the sapphires from Kashmir that are typically a pure, intense blue with undertones of violet, Burmese sapphires that range from a rich royal blue to a deep cornflower blue, and Ceylon or Sri Lanka sapphires (one of the oldest sources of these gemstones) that are light to mid-blue with a degree of luminosity.  The cornflower blue sapphire found at Yogo Gulch in Judith Basin County, Montana also has a strong following in the US.