gemologist

/dʒɛˈmɑlədʒɪst/
noun
  1. A person who studies or works with precious stones (gems), especially one who can identify, grade, and appraise them.
    • After years of study, she became a certified gemologist and opened her own jewelry store.
    • The gemologist examined the diamond with a special magnifying glass to check its clarity.
    • My aunt hired a gemologist to appraise her grandmother's ruby necklace.