Thread: The X-Hones

Got this stone in a box lot. Thought it was a vintage combo Coticule but not sure anymore. The lighter side is very soft and laps very easily, in fact will quickly clog 400 grit sandpaper with white slurry. Slurry has a strong alkali smell.
However no matter how hard I try with slurry or without, seems it won’t cut steel worth crap… no black stain in the slurry after many… many laps… haven’t tried shaving off it yet.

The dark side I think its slate, but it cuts steel quickly with or without slurry, slurry is gray or purple… slurry quickly changes from gray-purple to black after a few laps and you see new scratch marks in the steel.
The top is bone white, no stripes like other natural stones I have seen; bottom is slate gray and judging from the end seems to be a natural stone. The hone is glued.
5 ¾ x 1 ¾ x about ½ inch (145mm x 45mm x 16mm).

Not sure what this thing is… please help!