Why does my pearl have a spot of white in it?

[Lullabee]

I got these pearls at a market in hyderabad, but I just noticed this grey one has a spot of white in it. The white part also has no lustre.
Why is it that way? Does this mean it's fake?

 

[ennui]

Is it a chip, where the nacre chipped away from the nucleus?

 

[Lullabee]

Is it a chip, where the nacre chipped away from the nucleus?

I do not know much about pearls, so maybe?

 

[CortezPearls]

The photo requires better resolution to have an idea of what truly is happening there...it could be "missing nacre", but the shape (almost a perfect rectangle) makes me wonder...

 

[pattye]

I'm guessing this strand is alternating natural color and dyed freshwater pearls. Is there any difference in the level of the white area, or a noticable edge where the colors transition? Have you looked at the area through a loupe? For some reason this area didn't take the dye. It probably won't affect the wearability of the strand if the area is amooth.
A 10x loupe can be very helpful for checking all kinds of irregularities on pearls, looking down the hole to see nacre thickness, detangling knots if one strings pearls and so much more! Basic loupes are under $20.