Changes

'''Cleavage planes''' are common in [[crystal]]line [[mineral]]s.  They tend to follow weaker bonded lines through the crystal matrix, and lend a characteristic appearance to many [[minerals]] when they are fractured naturally or by a mineralogist.

'''Cleavage planes''' are common in [[crystal]]line [[mineral]]s.  They tend to follow weaker bonded lines through the crystal matrix, and lend a characteristic appearance to many [[minerals]] when they are fractured naturally or by a mineralogist.

The art of [[diamond]] cutting exploits the many possible [[cleavage planes]] in the [[diamond]] crystal in order to create a beautifully [[refraction|refractive]] [[gem]] from the raw [[material]].

The art of [[diamond]] cutting exploits the many possible '''cleavage planes''' in the [[diamond]] crystal in order to create a beautifully [[refraction|refractive]] [[gem]] from the raw [[material]].

[[Graphite]], a pure [[carbon]] crystal like [[diamond]], is so weakly bonded between its layers that the layers slide readily over one another; hence its use as a [[lubricant]].

[[Graphite]], a pure [[carbon]] crystal like [[diamond]], is so weakly bonded between its layers that the layers slide readily over one another; hence its use as a [[lubricant]].

[[Category:Geology]]

[[Category:Geology]]