Detailed Instructions: Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
Q: Context: Jon Krakauer, aside from the detailed recounting of the climb of the mountain in his book Eiger Dreams, mentions it briefly in Into Thin Air as one of his earlier difficult ascents (1992): ''I'd scaled a frightening, mile-high spike of vertical and overhanging granite called Cerro Torre; buffeted by hundred-knot winds, plastered with frangible atmospheric rime, it was once (though no longer) thought to be the world's hardest mountain''.
Question: What material was used for Cerro Torre?
A:
granite