An unique encounter during solar observation

[mrngbss]

I was observing the Sun this evening. While comparing and observing the Sun at 85x , I noticed a small rock-like piece rotating/tumbling across the Sun. It flew across the Sun in abt 5 seconds. It looked like a small rock (very tiny but clear), can see very clearly the smooth and rounded edges.

I thought it was a satelite but no wings and sharp point. Not a planet though, cannot be right? Was it a piece of space junk?

What could it be?