CRYSTALLOGRAPHY PART 7 (Crystal forms 3)

b)    Some common forms in the Isometric system

Cube: 

It is a form with 6 square faces at 90^o angles to each other.  Each face intersects 1 crystallographic axis and is parallel to the other two.  Its form notation is { 0 0 I }

 

Figure 29:  A Cube

 

Octahedron:

It is a form composed of 8 equilateral triangles.  These triangle – shaped faces intersect all 3 crystallographic axes at equal lengths (the same distance from the origin).  Its form notation is { I I I }. 

 

 

Figure 30:  An Octahedron

Dodecahedron (Rhombic Dodecahedron):

 It is a form composed of 12 rhomb – shaped faces each of which intersects 2 crystallographic axes and is parallel to the 3^rd axis.  Its form notation is { 0 I I }.

Figure 31:  Dodecahedron (Rhombic Dodecahedron)