This is quite a large Amethyst crystal with quartz inclussions - a statement piece. The crystal sits on a metal base consisting of a rectangular (almost square footer with a stem that holds the crystal). The base is included in the price.
 
Measurements (approximate but very close):
Weight: 323 pounds
Height:  The crystal alone is 36 inches and 59.5 inches with the base.
Width:  21 inches at the widest point.
Depth: 7 inches.
Base:  The foot of the base is 19" wide by 16.6" deep.
 
Amethyst is produced by the presence of trace amounts of iron and manganese in a clear quartz, giving the crystal its beautiful purple color.