Today I'm going to meet you to one of the most famous semi-precious stone Lapis Lazuli.
Is name is Latin for stone (lapis) and lazuli the region in which it was mined.
It's characteristic blue colour comes from sulphur 3 + ions.
It was known basically from the dawn of humanity, found in prehistoric figurines, Tutankamons mask, ancient Greece and was the most expensive pigment in Renesanse.
My specimen has some gold coloured pyrite, enjoy.