This may be a dumb question but I will ask anyhow.

How do you tell the difference between a Thuringian, Escher, and a hard black Arkansas stone?


I like to peruse the antique malls and I managed to grab a nice coticule, and now I've got me eye out for an Escher. You never know what will sell for cheap!

Anyhow, without lapping them, is there a way to tell em apart? I have a little pocket knife I keep with me to test hardness/finish of a given stone, but I really don't want another black Arkansas stone!

Seems like the colors are awfully similar.