GEM 230 MASTER INSTRUCTOR STUDY GUIDE

CLARITY CHARACTERISTIC: INTERNAL GRAINING

Instructor's Note:

Listen closely. The GEM 230 exam leaves no room for sloppy terminology, retail jargon, or guesswork. In the GIA laboratory, we evaluate and plot based on strict protocols. One of the most frequently misunderstood characteristics by novice graders is Internal Graining. Memorize this guide. You will be tested on it.

1. OFFICIAL CLASSIFICATION & DEFINITION

Characteristic Type: Inclusion (Internal)
Standard Abbreviation: IntGr
GIA Definition: Lines, angles, or curves caused by irregularities in crystal growth during the diamond's formation.

2. VISUAL CHARACTERISTICS (AT 10X MAGNIFICATION)

Internal graining is an optical phenomenon caused by a distortion in the crystal lattice. When you are on the microscope, you are looking for:

Texture/Appearance: Can appear as creases in cellophane, a thin sheet of reflective plastic inserted into the stone, or like vinegar mixed in oil.
Color/Reflectivity: It may be entirely transparent, reflective, whitish, or even colored (frequently brown).
Haze: In severe cases, heavy internal graining can give part or all of the diamond a milky or hazy appearance.
Instructor's Tip: Internal graining is highly dependent on lighting and viewing angles. You must rock and tilt the stone in the tweezers; it may disappear and reappear as the angle of light changes.

3. STRICT PLOTTING PROTOCOLS

This is where students fail. Pay attention to the plotting rules.

Plotting Color: RED. Because it is an internal characteristic (inclusion), any symbols drawn for internal graining must be in red ink.
To Plot or Not to Plot:
- Unlike crystals or feathers, Internal Graining is rarely drawn on the plotting diagram.
- The Comment Rule: If the internal graining is minor and there are other grade-setting inclusions present, you will typically omit it from the plot entirely and use the "Comments" section of the report.
- Standard Comment: "Internal graining is not shown."
- Grade-Setting Comment: If the internal graining is the primary reason for a lowered clarity grade (and is too dispersed to plot cleanly), the comment must read: "Clarity grade is based on internal graining that is not shown."

4. IMPACT ON CLARITY GRADING

You must understand how this inclusion interacts with the top-tier clarity grades:

Flawless (FL): A diamond with visible internal graining at 10x magnification cannot be graded Flawless. It is an inclusion.
Internally Flawless (IF): A diamond can be graded Internally Flawless if the internal graining is minor, strictly transparent, and does not pose a durability or severe transparency issue. It will be noted in the comments as "Minor internal graining is not shown."
VVS1 and Lower: If the internal graining is whitish, colored, reflective, or present in heavy masses that disrupt transparency, the stone drops into the VVS, VS, or even SI categories, depending on severity.

5. COMMON STUDENT ERRORS (DO NOT MAKE THESE)

Error 1: Confusing Internal Graining (IntGr) with Surface Graining (SGr).
- Correction: Surface graining is a blemish restricted to the exterior of the facets and is plotted in GREEN. Internal graining is an inclusion inside the stone and is associated with RED.
Error 2: Confusing Internal Graining with Twinning Wisps (W).
- Correction: While both are caused by crystal growth distortion, a twinning wisp is an actual amalgamation of pinpoints, clouds, or small crystals twisting outward from the center. Internal graining is purely the visual