At the beginning of Avengers: Infinity War, after Thanos announces that he is looking for the Tesseract/Space Stone, Thor informs Thanos that the Tesseract was destroyed on Asgard when Surtur carried out Ragnarök.
Would that have been enough to destroy the Tesseract and Infinity Stone inside, or could Thanos have have just swung by after the destruction and grabbed the Stone had Loki not swiped it earlier? The only indication we have that Infinity Stones can be destroyed is with the Mind Stone, and only because Scarlet Witch's abilities are derived from it, which wouldn't be applicable to Surtur and the Space Stone.