Diamonds are forever.

And if you've got the moolah, Grandma Lucy or Spike the dog can be forever, too.

Earth's hardest natural substance is made from compressed carbon, and an enterprising Chicago company uses intense heat and pressure to grow diamonds from the carbon ash of cremated remains — human or animal.

The only difference between this synthetically made bling-bling and its naturally occurring cousin is a few hundred million years. LifeGem's quarter-carat to 1.3 carat diamonds are ready in around five months and range in price from $2,199 to $13,199.

Last year, the company sold 500 of the canary yellow beauties.

The gems' color comes from trace elements left in ashes. Nitrogen turns a diamond yellow or brown. Then, depending on how it's cut, the diamond can appear pink. LifeGems range from yellow to orange, and other colors are in the works.

A heartbroken widow says her husband's LifeGem will be a godsend.

"It was last November when they started the process," said Carol Thorndyke, 56, who expects her $3,000, princess cut, sunset orange diamond sometime in early summer. "I'm hoping the color will turn out the way I want."

Thorndyke heard about LifeGem on late-night television. She had her sons look for it on the Internet.

Her husband Gerald, who died in early 2003, wouldn't mind, she said. "I think he would probably laugh and just say, 'Oh that's a great idea.' "

PetGems are rising in popularity too. So far, the company has turned dogs and cats into diamonds, but they are also fielding numerous calls from horse owners, said company CEO Greg Herro.

"Less than 10 percent of our orders are pets," Herro said. "It's a newer idea."

Owners would have to take their animal to a special crematorium for the cremation. Pets also come out with yellow tones.

LifeGem offers the service through 314 funeral homes across the United States and at least a dozen total in Hungary, the Netherlands, the United Kingdom, Australia, Canada and South Africa.

"If we would not have thought of this, somebody would have eventually," said Dean VandenBiesen, the company's vice president for operations. To create a LifeGem, the body is cremated by regular means.

A technician collects 8 ounces of the remains and mails it to LifeGem headquarters just outside of Chicago. (An adult human body yields enough carbon to make 50 stones.) Unused cremains are returned to the family.

LifeGem separates the carbon and sends it to an undisclosed lab on the East Coast. There, a specialist heats the element in a low oxygen environment, which turns the carbon into a pure grade of graphite. (The stuff found in a pencil tip.) Sometimes extra graphite is added.

The graphite is placed into a diamond press and subjected to about 3,500 degrees of heat and 800,000 pounds of pressure per square inch.

A crystal is grown in six to eight months. The larger the diamond, the longer the gestation.