Sandstone sharpening stone? What is it?

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This stone was in an old wood worker's shop in Hudson, New York, not far from Norton in Troy, NY. That does not mean the stone was manufactured by Norton, but proximity brings it to mind.

The stone was a slimy black brick when it was given to me - coated in oil and dust. It is fairly coarse. It feels like about #400 grit and is porous. Oil or water soak in quickly.

Does anyone know what it is? Could it be Hindostan?

it has the characteristic look of sandstone but so does alot of other stuff. Sandstone is pretty friable meaning if you rub it with your hand the particles will come off. It's pretty granular. It's also very porous.