Unknown vintage natural sharpening stone

Unknown vintage natural sharpening stone. Tested on a straight razor - Naniwa 5000 grit (several photos with different lighting), stone with suspension, pure stone (used as a water stone) and photo - used as an oil stone. Tried shaving - very uncomfortable - seems to be coarse graininess - no more than 4-5 thousand grit.

[@Legion-it6db]

The grain looks like it could be a Turkey stone.

[@Martins-Shaves123]

Water of ayre, or Tam O Shanta would be an excellent find , especially that size ...hope you'll know when cleaned and lapped flat.🎉

[@filaptv]

Yea man i wanna know what that is too. I wanna find some old school/medival east or west european sharpening stones for tools and or swords.