How does GIA know where the diamond was mined?
GIA identifies the country of origin by requiring the diamond be received and examined in rough form in a sealed, tamper-proof package directly from the mine. Data is collected on the rough and each rough is assigned a unique identification number. After the diamond is cut and polished during the manufacturing stage, the manufacturer submits the polished diamond to GIA, along with the assigned identification number from the rough. GIA then analyzes the rough and polished data to scientifically confirm that the data from the polished diamond matches that of the referenced rough.