Lawn Mowing Surprise

[jay]

While mowing my lawn recently, I observed a sudden puff of black fibers come out from under the mower.
At first I thought I ran over someone's black Covid-19 face mask.

What was this?

I checked the debris.  The fibers stained my hand a light shade of black.  I then found part of a shattered tube from a Sharpie Pen.
I never knew a Sharpie pen had fibers inside.