Thread: Scored a 50 cent stone. Soft Ark?

I was at the surplus tool place again today. He's got a big box of stones for 50 cents each, mostly small, all salvaged from industry & soaked with oil. I got a couple small triangular cross-section stones for sharpening serrations. But then there was this big honker with the corner chipped off.

I can't pass up a 50 cent stone, so I bought it, lapped it, & sharpened a kitchen knife with it. It's finer than my homemade slate hones, but too coarse for a razor (except maybe bevel setting). It feels hard, but must in fact be pretty soft, because it was dished out on both sides before I lapped it. What do you think? Soft Ark? It seems a little coarser & more aggressive than my other mystery stone which most people here thought was a soft Ark, but definitely in the same ballpark.