Probably not. Diamonds are not forged, diamonds are cut.
If you could find a stone that large, and were willing to pay a diamond cutter to plan and cut such a stone into a circular ring, you'd truly have a one-of-a-kind treasure. However, the chances of one erroneous cut, which would destroy the stone, are probably high.
(Unfortunately, you'd never be able to change the size of the ring.)
Alternatively, with a stone that large, you could commission a diamond cutter to plan and cut the stone as a gemstone, and sell it for more than you paid for it.
Update as of March 2012
A ring, cut from a single diamond has been produced and made available from Shawish Jewelers in Geneva for about US$70,000,000. You can read more about it, below.
The diamond ring in question was made in January 1965.
Usually a noble metal, such as gold or platinum, and a diamond stone.
The biggest diamond ring ever made is called The Spirit of de Grisogono. It weighs 312.24 carats, or 62.45 g. It is also a black diamond and is the largest black diamond ever found.
A diamond ring is composed of a diamond or multiple diamonds, and a metal band.
Usually a diamond ring is manufactured from metal, including gold, silver, platinum or other metal, and set with a diamond.
Add a diamond and have them made into a patriotic ring.
In Kenya, of course! :D
Unfortunately as far as I know, you cannot forge the ring as it has no real ability.
Solitaire is a style of setting for a ring: it provides one setting for a single gemstone. A 'normal diamond ring' can be any kind of diamond ring setting. A diamond is a diamond, regardless of its ring setting.
Diamonds are seldom permanently mounted, as this could damage their value. To change the diamond or the ring, go to any jeweler who makes custom-made jewelry.
ring pops are made out of artificial flavored goo. they insert the goo into a cut out of the diamond ring then they put the actual round about ring in the stencil they let the goo harden and it becomes an enjoyable candy.
Well no not really. The cost of a diamond is usually independent of the cost of a diamond ring setting. The only relationship I can think of between these two values is when a diamond is fancy cut, has an unusual shape or is very large in size. In that case, a run of the mill ring setting may not do, and you may need to have your ring setting custom made in order to accommodate an unusual diamond.