Cleavage Fractures or Transgranular cleavage are a type of brittle fracture that occur across crystal planes.
The separation of the two fragments occurs via tensile (perpendicular pulling) forces.
Macroscopically: (Possible to see without the need for a microscope) The fracture surface may show a grainy or faceted texture as a result of the fractured crystal orientation.
Intergranular fractures are brittle fractures that occur along grain boundaries, this often follows enbrittlement or weakening of grain boundaries through stress concentrations or from growth of other crystalline phases due to changes in conditions.
As seen above the fracture can undergo significant changes in direction, in direct comparison to transgranular fracture.