There has been much discussion on buying cut stones lately. People
can look at two stones (same material, color, clarity) and often one
will look much better that the other, but most do not know why. This
(what the differences are) is something everyone should be aware of.
Most that has been recommended will not have these problems, still if
you know this you will also know why some, same color and clarity
also will cost more than the other.
http://www.theimage.com/faceting/facet5a.htm
The above stones are, unlike the first, are well polished, however
still show optical problems.
http://www.mikesgems.com/page.html
http://www.rockhounds.com/rockshop/gem_designs/bow_tie_blues
http://www.creativecutgems.com/comcut.asp