Color : Varies from greenish blue to sky blue shades
Hardness : 7

Blue topaz has a definite, uniform color ranging from sky blue to Swiss blue. It is sometimes confused with the more costly aquamarine - yet whereas aquamarine sometimes has a greenish-blue or bluish-green tint, blue topaz will always look blue or bluish gray. The one exception is for surface-enhanced topaz, a process introduced in 1998 that enhances the stone's appearance and brings out colors such as blue to greenish-blue to emerald green.