New, Unused [Ink Stone Material, Stone Material, Chinese Natural Stone? 9 Items Together]

These are inventory items from an acquaintance's sole proprietorship business closure.

They are new and unused, but have been stored long-term at their home/store.

They are likely natural stone seals made in China, but I lack the expertise to provide specific details.

The sizes, from left to right in the image, are:

* 43 x 12mm
* 45 x 12mm
* 49 x 15mm
* 50 x 15mm
* 51 x 15mm
* Same as above
* 56 x 17mm
* Same as above
* Same as above

A total of 9 pieces.
*Please allow for slight measurement errors.*

Thank you for your consideration after understanding the above.