Consider that diamonds are really carbon that's been subjected to great pressures. You're carbon, too. So a company called "LifeGem" will take your remains and make you into a diamond. As they put it, "diamonds from ashes are created from a very specific source of carbon - your loved one." Really??
In nature, the forming of a diamond takes a very long time. However, with modern machinery diamonds can be made quickly and easily.
One company has a novel source for the carbon that will be used to create a diamond: you.
The company wants you to order that your remains be cremated and turned into a diamond that will last forever. This story was recently reported in Big Canoe News article titled "Diamonds (and you) can be forever."
As you read the original article, you will discover this is not the only company that offers to let people do something unique with their remains. Another company will even press your ashes into a phonographic record that can be played. Yet another company will make your ashes part of potting soil in which your relatives can grow a plant.
For most people this is probably in the "well, it's good to have options, I guess" category. On the other hand, if you do want to have something unusual done with your remains, it appears that you have several choices.
As you may imagine, it is important to have anything unusual spelled out in your estate plan. Do not just tell someone what you want done. If you want your plan to carry weight with the court, let alone your family, it needs to be written down officially.
Consult an experienced estate planning attorney to ensure your wishes are honored.