Congratulations! You have found a London Blue Topaz gemstone! Blue Topaz has become the 2nd most popular colored gemstone (sapphire is consistently number one).
This is not surprising. Topaz is a very hard material --8 on the Mohs hardnes scale -- and blue topaz is a very pretty stone, available in a wide range of vivid hues with a striking luster.
Naturally occurring blue Topaz is quite rare. Typically, colorless or pale topaz is heat treated and irradiated to produce a more desired darker blue color. Blue Topaz is the state gemstone of Texas, and light blue Topaz is found in the granite in Mason County, Texas. Topaz is associated with igneous rock and is found around the world.
While topaz is very hard, it is not the most durable gemstone. That's because it has perfect cleavage, a property it shares with diamond. That means it can be chipped or split by a sharp blow, so it should be protected from hard knocks.