Internal Graining:

Internal Graining are lines, Angles or curves that might appear whitish, colored or reflective or affect transparency at 10X, caused by irregularities in crystal growth. Internal Graining are not invisible to the naked eye.
We do provide grades for Internal Graining in the stones. Internal Graining also affects the face up look of the stone. Thus becomes important to grade them.
We grade Fluorescence as follows:

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IG 0 indicates No Internal Graining.
IG 1 indicates very light internal graining. They are not easily visible. We have to search them precisely through 10X loupe. Thus it doesn't affect Face up look of the stone to the great extent.
IG 2 indicates Medium Internal Graining. They are easily visible through 10X loupe.It does affect the Face Up look of the stone.
IG 3 indicates Heavy Internal Graining. They affect the overall Face up of the stone. Sometimes in higher clarity grade due to its heavy impact Clarity of the stone is also downgraded.
{Note: We grade Internal Graining in the stones having Clarity SI3 & better towards VVS1}