There are 2 types of non-natural diamonds. Natural diamonds that have been altered and non-natural diamonds produced in a laboratory.
1. Natural diamonds that have been altered (or, “clarity enhanced” diamonds)
Today we are able to take a diamond that has a large eye visible inclusion and remove it with a laser, which leaves a hole in the diamond the size of the inclusion or a pinch larger. It is filled with a molten glass and boron solution, allowed to harden and then re-polished so you cannot see where it’s been done.
It is illegal for a jeweler to not disclose that this type of stone has been treated. However, in my experience I have seen many stores not disclose this to customers, or if they do, they dream up a flowery story to explain its lower price.
I’ve heard salespeople use a line such as…
“This diamond has been improved by removing some of the inclusions so you can no longer see them.”
Everything sounds good until you hear a more realistic version of the story, which might go like this…
“We have had the eye visible inclusion removed in this diamond and refilled with glass, which will slowly change color to a grayish tinted area with exposure to UV rays (mostly sunlight). The stone will not have any resale value due to its alterations and unpleasant appearance.”
Obviously my recommendation is to stay far away from diamonds with this type of treatment. Despite manufacturer claims that this type of treatment is a permanent solution, this technique has been judged to be non-permanent (because the glass will change color) by a number of gemological institutes.
In addition, “clarity enhanced” diamonds cannot be exposed to acid cleaning or a torch flame. Therefore, should your prongs need re-tipping or your ring cleaned with an acid treatment, the stone must be removed and then re-mounted after the work is completed. Basically, it will cost you more money.
2. Non-natural diamonds made in a laboratory
These are fine quality stones and should come down in price in the future. Right now they are expensive enough that you might as well buy a natural. I would wait for them to come down to about $250-$500 per carat. Currently they are about $4,500 per carat for a decent looking one, and you sure don’t want to pay $4,500 and in a couple years have it only be worth $500.
The Cubic Zirconia is an example of this. When CZ imitation diamonds came out they were $250 per carat and now they are about $2 per carat.