Diamonds are worthless and will be even more so in the future.
The companies Gemesis and Apollo Diamond, which are in the USA, have technology to produce 1-carat diamonds for less than $150 each.
Apollo Diamond could manufacture diamonds for $5 a carat.
Read all about the story here:
http://www.wired.com/wired/archive/11.09/diamond.html?pg=1&topic=&topic_set=
(A favorite DVD of mine is a 1998 French film (English subtitles) called Place Vendôme. It stars an aging and alcoholic Catherine Deneuve character who is involved in the glamor jewelry trade and gets crosswise of De Beers over some pilfered gems. It is a very stylish film with a somewhat murky, though sophisticated, storyline. An interesting peak into the gem trade.)
....not only that, but DeBeers has a 15+ year supply already mined, cut and polished. There's a diamond glut.