A spare set of stones came with another set I bought some time back, and they're very... irregular, I guess you could say. The shape is fine, about 6mm, and there aren't too many chips, but there are all sorts of spots, dots, and marks that kind of look like stains?

I'm curious if any of you good folks can tell me whether these could be cleaned up (with hydrogen peroxide?), or if this is just how they were made. Any idea how these marks come about? Or whether it's a species of clam (or part of the shell), that shows this sort of coloring?

Maybe not so easy to tell if they're coffee stains or natural patterns --
I remember Mr. Kuroki used to have some 'novelty' shell stones with similar purplish/magenta hues --
something must be in the waters during the formation of the shells --
if they don't come off easily with soap, maybe H₂O₂ is a next try...

Hello,
These are flower grade Suwabute (Native Japanese clamshell). Flower grade is the native clamshell equivalent of Standard/Practical (Jitsuyo).

The coloring is natural and won't some out with hydrogen peroxide.

Hyuga shells are rather colorful with shades of orange and surface purple.

Here's a photo of what most hyuga shells look like unprocessed.

http://shop.kurokigoishi.co.jp/upload/i ... =671_2.jpg

These stones are graded based on color more than by grain (since the grain is fine throughout). White (with a tinge of orange) is snow grade. More orange is moon. Highly noticeable is flower.

Here's a good photo of flower grade stones from Mr. Kuroki's site for comparison.



Hope that helps

Ah, thanks! Very interesting that they're graded by color. I hadn't known suwabute stones all had the same stripes, either. A happy accident that these were 'left over' then, I'll enjoy knowing their source

Erythen, Thanks for the info.