honed slate is gritty to the touch

    I've had a honed vermont green slate kitchen countertop for about 3 years. From the very beginning it has always felt as if there has been a layer of grit or sand on top, even after I have washed it. It isn't sealed. It seems to be completely non-porous and has very few scratches, but within seconds of my cleaning it (with a stone cleaner or just water and a microfiber cloth) it feels gritty again. When it was installed the fabricator did say they had a hard time honing it-however it does feel flat and even - just with a light coating of powder on it all the time. Does anyone have any idea what causes this and what I can do about it? Thanks!