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Do Not Use A Sharpy.. Some stones will never lose the image left by absorption of the ink. Coticule and shaptons and some manmades and some other naturals eat the ink and there you have it for a...

And lapping it can be a many sittings job! They be really hard but use a lot of coarse grit sanding paper to get the surface level.
I usually start with dry sanding with some dry wall sanding mesh...