pentagonal crystals

[William Tivol]

MKHESS (mkhess at aol.com) wrote:
: Are there any common chemicals (or uncommon if need be) that produce
: macrocrystals that are pentagonal? Its a long story, but my interest has
: nothing to do with anarchy or witchcraft. Help anyone? MKHESS at aol.com

	No, there are no pentagonal crystals, because there is no way
to tile a plane with repeating units with five-fold symmetry.  However,
there are materials which form quasi-crystals with five-fold symmetry.
they consist of two (possibly more?) types of unit cell--a simple case
has two different rhomboids.  Examples of this kind of material are
Al-Ni-Fe, Al-Cu-Co and Al-Ni-Co alloys.
				Yours,
				Bill Tivol