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Choosing Diamond Master Stones for Color Grading | How to Choose Masters

We can select our own diamonds to send to GIA for a master stone report. It’s important to understand that specific requirements have to be met before GIA will accept a stone as a master.

Choosing master stones is a task in itself. Unless you have a lot of contacts in diamond suppliers, finding the prerequisites required for a master stone will be difficult to say the least. There will definitely be a hefty premium on a single or a set of master stones, so be prepared for sticker shock.

Avoid:

  • Thick to Extremely Thick Girdles
  • Crown heights less than 11%
  • Pavilion depths less than 40% or greater than 45%
  • Old style cuts
  • *Damaged stones or dirty girdles
  • Medium to strong fluorescence
  • SI2 to Imperfect clarities visible through the pavilion with your naked eye

Accept:

  • Thin to slightly thick girdles (faceted is ok)
  • Crown height 12% to 15%
  • Pavilion depth 42% to 44%
  • Modern round brilliants
  • A stone without damage and clean girdle
  • None to faint fluorescence
  • SI1 or better, without dark inclusions

*Faceted girdles are preferred since gray girdles will collect embedded debris in pits caused in the cutting process leaving behind an unwanted color influence.

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