Brownish yellow inclusion in sapphire

Hi everybody,
I bought this natural (so it was certified) steely blue sapphire from Tanzania.
The gem is very nice and sparkling. Under the loupe I noticed a small, brownish inclusion in the right side of the stone.
I examined the inclusion under microscope, in immersion, x 100.

Might you be so kind to give me an idea about the nature of this inclusion (i.e. fracture in the crystal)?