Take context from the input text and decide on the accurate relationship between 'Xstrata' and 'Glencore' from the options provided.
Options: operator, owner of, stock exchange, owned by

Having transformed Glencore from a poorly understood commodities trader based in Baar into one of the world's largest resources companies through the spectacular $US60 billion float four years ago and the takeover of mining group Xstrata in 2013, the hard-nosed South African was lauded as a savvy deal maker.
owned by