About Gemstone : Topaz
Topaz, said as the birthstone for people who born in November, is well known for Yellow and Blue Color.
Which in fact have many color like pink, yellow, golden brown, orange, blue, even colorless.
Blue topaz are rare in nature and usually heat treated so it's become dark, deeper blue.
In term of mohs scale, Topaz are pretty hard, it's number 8 at mohs scale.
So it's harder than steel nail and almost as hard as masonry drill bit. Wow..
And you should know that Topaz don't have that high refraction index, so it's may not be that sparkle like diamond, instead, have more of calm and elegant shine to it.