Beautiful blue tanzanite. Internally flawless or close to it. IF quality. Extremely clean looking when viewing with jewelers loupe. 10 x internally flawless it looks to be upon examination. Very reflective stone. No apparent window which is often seen in tanzanite cut stones.
Round cut tanzanites are normally harder to find as tanzanite rough crystals are rectangular in shape and lend themselves more to ovals and rectangular cushion cuts. Rounds have a greater loss of weight when cutting called facet rate. They tend to be a little pricer as a result and rounds are normally the most sought after shape in a gemstone.
Certificate is online verifiable using the square through the photo function of your camera. It automatically brings up the certificate through the website.
When heated to 750 to 900 F or 400 to 500 C the brownish tints vanish and the tint of blue deepens.

Before heating the stones are trichroic which means three different colors depending on the direction you are looking at the stone. After heating the stones become dichroic which is two different colors. The best of the best is royal blue when viewing down at the face of the stone. Some tanzanites show royal blue from all directions. I'm not the best at taking videos or photos.
This stone is masterfully cut without window. Full reflection.