Inclusion. A small internal characteristic — a crystal, feather, cloud, or pinpoint — formed inside a diamond during its growth. Inclusions are how clarity is graded; their size, number, location, and visibility determine where a stone lands on the FL-to-I3 scale.
Most inclusions are invisible without 10× magnification. A stone described as 'eye-clean' has no inclusions visible to the naked eye at normal viewing distance.
Inclusion location matters as much as size. A small inclusion under the table is far more visible — and more discount-inducing — than a larger one near the girdle.
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