What is capable of being split, cleft, or divided in the direction of the grain, like wood, or along natural planes of cleavage, like crystals. This crystal is a pellucid, fissile stone. Sir I. Newton called?

fissile — Capable of being split, cleft, or divided in the direction of the grain, like wood, or along natural planes of cleavage, like crystals. This crystal is a pellucid, fissile stone. Sir I. Newton. (Webster's 1913.)