There are many stones that are gray but are not Thuringian.
This one is dark brown and makes yellow slurry.
Originally Posted by UrsaMaior
Looks like brown Thuringian.
Originally Posted by Scipio
This is what I believe is a Brown Thuringian. Although the base colour on mine differs, it has those similar orange/pink markings. An authority on hones has used mine and believes it to be a Thuringian.[/ATTACH]
It doesn't look like my Thuringians with brown patches, nor like my Vosgiennes (Vosgienne is in my opinion a correcter name for 'Brown Thuringians'). They are a very uniform purplish brown (see also here and here).