Check for a laser inscription on the girdle
Use a jeweler’s loupe to inspect for natural inclusions
Look for sharp facet edges and strong brilliance
Test with a thermal conductivity diamond tester
Verify the stone with a gemological lab report
Examine whether the diamond fogs briefly and clears quickly when breathed on
Check for double refraction signs; diamonds do not show it
Compare weight and size against known diamond measurements
Inspect under UV light for fluorescence
Have a certified gemologist confirm authenticity