Search:

try to enlighten your stone like this:
//where it was?...mmm.. ok, here it is:
197909
Washita is semitransparent (may be slightly, may be not).
Hindostan\sandstone is not.

Actually, hindostan isn't a smthing unique.
More about that http://straightrazorpalace.com/hones/85253-another-mystery-hone-thread-2.html#post984160
and...

2 doorsch: Sorry, can't understand:
do you mean that it's a hindostan in your picture?
Could you show more pics with other sides and with bigger magnification?

peak 2008-50 is a microscope Depth Measuring Microscope Peak 2008(DMR) 25x to 100x Peak Optics, Magnifiers, Comparators, Loupes, For Inspection & Measuring, 2x to 300x

These two photos have been...

Under the peak 2008-50 the difference is clear enough:
washita
197792
more pics https://fotki.yandex.ru/users/beavers-net/album/357790/
hindostan
197791
more pics...

Looks like a washita..
Did you get slurry from it by using a diamond plate?