They made them into pestles to bruise pepper and herbs for their sauces.
Source, in full
Historia Albigensis, ch. 46. Terror of the routiers. "Another of their delights was to pollute and break in pieces the images of Christ, to break their arms and legs, and ill-use them."—Jules Michelet, History of France, tr. G. H. Smith (New York, 1882), vol. i, p. 275