The company that started this trend, I believe, was
http://www.lifegem.com . 
They create diamonds from human as well as animal cremation ashes.
There used to also be gemstones available at www.ashestoashes.com .

A quick google search using the random terms "cremation" and
"gemstones" or "jewelry" brought up many sites - not only those that
will create gemstones from the "cremains," but those that have nifty
little pendants of gold, silver, platinum, etc., in which a tiny amount
of cremains can be placed so you can wear them always. This option
tends to be much less expensive than the creation of a diamond or
other gemstone from cremains, although I still think the latter is
an absolutely lovely idea!

Sydney

[Posted in FML 5938]