Grading Equipment

Good grading is repeatable grading, and repeatability comes from the bench. The equipment of a professional diamond grader, gathered over years, lets the same stone read the same way twice.

The grader’s bench

• 10× magnifying loupe — the standard for clarity, by international convention
• Carat balance — for weight, to a hundredth of a carat
• Hydrostatic balance — for specific gravity (diamond reads 3.52)
• Leveridge gauge — for measurements, often electronic
• Diamond-grading daylight lamp — producing diffuse, neutral light
• UV lamp — for fluorescence, ideally with a fluorescence comparison set
• Comparison set — clean master stones spaced at intervals for colour
• Hearts & Arrows viewer — for optical symmetry
• Proportionscope — for reading proportions
• Spectroscope — for absorption spectra and type
• Microscope — for advanced research and detection
• Low-magnification lenses (a binocular forehead loupe) for general work
• Tongs and a cleaning cloth, and white folded paper to rest the stones on