Sapphires come in many colors. The most popular of which is blue. Common to all colors, there are two traits to generally establish value, color intensity and clarity of the stone.
An intense blue sapphire with established provenance of Kashmir with no disturbing inclusions can be worth several hundreds of thousands of dollars per carat. While a very similar synthetic sapphire can be purchased for twenty five dollars per carat.
When purchasing a sapphire you must first establish what color sapphire you are looking for. Then set about determining your budget. Finally, and most importantly, select a merchant who is knowledgeable and can provide a variety of sapphires for you to choose.
Valuable sapphires should be accompanied by a grading certificate from either the Gemological Institute of America or the American Gem Laboratory, both respected and professional organizations. International laboratories which are also recognized are Gubelin, SSEF, and GRS.Sapphire Article GIA