Tendency of a Mineral to Break Along Smooth Lines

This page is the CodyCross answer for the clue below from London, Group 499, Puzzle 5 (Portobello Road Market).

Question is: Tendency of a Mineral to Break Along Smooth Lines

and the answer is: CLEAVAGE

Word Meaning:

CLEAVAGE — The act of cleaving or the state of being cleft.

Definitions from Wiktionary.