Polyhedral framework .
     The polyhedral framework model of FCC elements is identical to the lattice model .
which can be envisioned as the space filling of tetrahedra and octahedra in a ratio of .
2:1 shown previously. .
. .
Cleavage .
     The cleavage of a crystal refers to its tendency to be split apart along certain .
preferred planes which are often parallel to the orientation of its most densely .
packed layer(s).  Since the closest packed (111) layers of atoms of the FCC elements
interpenetrate each other, their crystals do not have distinct cleavage planes.
Crystal habit
     The habit of a crystal is its propensity to assume a characteristic outward shape
as it grows.  As mentioned previously, this depends on its internal lattice structure
as well as the particular chemical and physical factors present in the immediate
environment of the growing crystal.  As a result the crystals of most elements and
minerals have several common habits.  The characteristic crystal habit(s) of a group
of structurally similar elements or minerals is usually represented by a member of
group that best displays its properties.  For the FCC elements this is gold.





not shown

Ex. Au











Figure 46 -  Crystal habits of FCC elements


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