The value of a diamond is predominantly determined by many qualities that, together, determine its uniqueness relative to similar other diamonds.
Only a qualified gemological appraiser can determine the value of a given diamond with accuracy.
However, you don't need an appraiser's report to get a good understanding of how pricing works. The best way to get started in understanding diamond prices is simply to look at diamonds and their prices. Diamond Review's multi-vendor Diamond Finder is an excellent tool that allows you to compare and view diamonds from many different vendors. To try out Diamond Finder, click here.