If you could tell me the size of the main stone, in millimeters, I could start. However, the main determining factors of diamond are their color grade and clarity. Size above one carat becomes a major value factor as well. $1400.00 a year ago? With an appraisal from a GIA certified appraiser (make them show you their certification along with valid ID), you might get lucky and recoup 8 to 900.00 through a private sale. If you hold onto it for 10 or 20 years you may get your full purchase price back, plus a little more. Assuming the market for diamonds keeps going up. Right now being white gold instead of yellow is considered a plus.
BTW, expect an appraisal to cost you $60.00 to $100.00. Also, unless you are sure you will never get married, keep them for the right person. Much cheaper in the long run. Resizing to fit the finger will only cost around $100.00, instead of another $1400.00 plus. Get the appraisal either way, and don't lose the paperwork this time. If you have homeowners insurance, or renters insurance, send your insurance company a copy of the appraisal and see how much the insurance rider will cost. You decide if it is worth paying for.