How Ultron find the mind gem in Avengers

At Avenges Tower in Age of Ultron we see Ultron steal the sceptre from Tony's lab.

Inside that blue “orb” was the mind stone as we see in this scene where Ultron removes it from the sceptre.

Ultron managed to extract said stone and implant it in Vision, who was created by Tony, Banner and Helen*.

*For those who don't remember, Helen Cho was the Korean scientist who healed Hawkeye and helped create the Vision. She had been made by Ultron to download his consciousness into the Vision.