How does crystal structure determine mineral cleavage?

Question

Jonathan Avila · Accepted Answer

every crystal structure has a definite shape like
cubic ,hexagonal ,FCC etc

A plane named cleavage plane is present in every crystal system

So due to the particular type of crystal plane the mineral which has the crystal system cleaves only in a particular direction

#In# # cubic# # system#
the cleavage occurs in {001} planes

In #hexagonal#(basal clevage) and #Rhombhohedral# clevage occurs in {0001} planes

in FCC cleavage occurs in [111] plane

Diamond which has Octahedral cubic has Octahedral clevage

for planes of hexagonal system refer (Miller-Bravias Indices for Hexagonal crystal sytsem )

Audrey Adams · Answer

undefined Crystal structure determines mineral cleavage because the arrangement of atoms or ions within a mineral's crystal lattice dictates the planes along which the mineral is likely to break when subjected to stress. Minerals with cleavage have planes of weakness in their crystal structures, where atomic bonds are weaker than in other directions. The number and orientation of these planes of weakness are determined by the symmetry and arrangement of atoms or ions within the crystal lattice. Minerals with different crystal structures exhibit different types and qualities of cleavage, ranging from perfect to poor.