I thought that it a charnwood. They hadn't got control of Arkansas so I'd guess it would either be European (and something popular at the time) or the New York and Vermont slate that was commonly used as building materials. We must not forget that whetstone(especially natural razor hone) were usually an of shot of another industry be it chalkboards, paving stones, billiard tables, ect. I suspect that the grind stone companies that began selling razor hones out of the same quarries that they pulled grind stone from and either the layer or random inclusion of a more rare mineral was to slow or fine for grindstone and it was alternatively marketed. It's a tale as old as time. In most societies(especially throughout the past) priority on tools usually went to the men building things and those men needed sharp tools to make work move. Generally these laborious were the same men finding and pulling the dang rocks out of the ground. I know most blue collar types generally wear beards to some degree, at least most of my life, especially people who are miners or some similarly dangerous job where shaving just does not matter when you might die. I could see them prioritizing the folks THEY need to continue building and expanding and getting paid VS those who like to look neat. While I was daydreaming this scenario I can see many way of how razor hone business was just the scraps they were using to keep in the black.I was trying to see what the stone was in GW's kit. Coticule maybe?