From Wikipedia,
the free encyclopedia
In
crystallography, the
rhombohedral (or trigonal)
crystal system is one of the 7
lattice
point groups. A crystal system
is described by three basis
vectors. In the rhombohedral
system, the
crystal is described by
vectors of equal length, all three
of which are not mutually
orthogonal. The rhombohedral
system can be thought of as the
cubic system stretched along a
body diagonal.
In some classification systems,
the rhombohedral system is grouped
into a larger
hexagonal system.
There exists only one
rhombohedral
Bravais lattice.
The
point groups that fall under
this crystal system are listed
below, followed by their
representations in international
notation and
Schoenflies notation, and
example
crystals.
| name |
international |
Schoenflies |
example |
| rhombohedral holohedral |
 |
D3d |
calcite |
| rhombohedral hemimorphic |
3m |
C3v |
tourmaline |
| rhombohedral tetartohedral |
 |
S6 |
dolomite |
| trapezohedral |
32 |
D3 |
quartz |
| rhombohedral tetartohedral |
3 |
C3 |
|
