This is because a bonded jeweler has a refund policy on the diamonds you purchase so if you buy one, you can return it any time for a one hundred percent refund. Non bonded diamonds do not have the same policy attached and you will have to be wary of the reasons behind that.
Bonded diamonds are not treated and they are completely natural so the jeweler who shows them to you feels confident enough to sell them with a breakage policy. This means, should the stone break or chip, the jeweler will replace the diamond one time for free.
The value of a bonded diamond has a fixed appreciation rate to keep pace with inflation. So, the bonded diamond’s value would increase over time. This usually applies to the trade in diamonds not the buy back diamonds. In addition, you will be protected in the event that there is a market crash. In this situation, as you would expect, the value of the diamond would naturally decrease but if you had dealt with a bonded jeweler you will be able to get a refund of what you originally paid for minus the current price of the diamond.
To locate a local bonded jeweler ask around in your local stores if that proves to be difficult try searching the internet or go back to your local jewelry stores and ask for referrals. If that doesn’t work, tell the jewelers you are dealing with that you will only buy bonded diamonds.