I've had a sililar problem with my "lithide" hone, also from tilly.
I actually went to the great length of using a piece of oak to lap it because I thought it was getting grit stuck in it from other hones.

After 11 hours (thats right) of lapping it was still rough. Closer inspection with a loop revealed little gold colored inclusions.

I do however have a few "practice" razors, so I tried one on it and the inclusions seemed to come loose.

It still works as a finish hone for me