How do blemishes affect diamond grading, if any at all?

• A. Blemishes very rarely have an effect on grades lower than IF.
• B. Blemishes very rarely affect grades lower than IF.
• C. Blemishes always affect the grade.
• D. Blemishes never affect color grade.

Answer: (B)

Blemishes are external surface flaws that are considered when assigning a diamond’s clarity grade, but they are not the main factor once internal flaws are present. The highest clarity levels (like Internally Flawless) are defined by the absence of internal flaws, and any blemishes on the surface are tolerated only up to a point without necessarily downgrading the grade. When a diamond has internal inclusions, those internal features dominate the clarity assessment, and surface blemishes usually don’t push the grade down unless they are quite significant. That’s why blemishes very rarely move a grade below the top tier; the internal flaws are the primary determinant in that range. Also, blemishes don’t affect color grade, because color grading evaluates body color rather than surface characteristics. So, blemishes can influence clarity, but their impact on grades below IF tends to be minimal unless they are substantial.