Ardennes has stones marked standard, select and select plus. They claim the only difference between standard and select is appearance and all have grit ratings between 6k and 8k. The select plus are from veins known for superior razor honing capability.

They also have unmarked coticules and BBSs they recommend for use on tools. Cotis were also used to keep carpentry tools true and sharp.

I have been lucky in that all the coticules I have produce a decent edge on my razors, but some are clearly superior to others. I go on the assumption that the edge I get from a coti is from a hone in the 6K range and use a finisher or chromium oxide pasted strop after that.

They are natural stones and can vary significantly. In my experience, lapping a coticule is useful for ensuring you have a flat starting surface, but it won’t impact the abrasiveness. The garnets in the coti are the shape, size and are distributed how they are and lapping will have no effect on that. Some are hard, don’t self slurry and can be excellent finishers while others are soft and slurry easily and can be used to reset a bevel.

Articles I’ve read indicate there is greater variation in abrasiveness and hardness amongst coticules than can be found in BBWs even though they come from the same quarry.