how do you clean stained soap stone?

Question

i have these soap stone chess peices, and some are brown, so it is not so noticable but the light green peices are stained yellow of ciggerette smoke.
i would like to clean them, because when i pull them out to play i become quite dissapointed
they were on display in my parents home for years and years, and they smoked a heck of alot.
gone from green to yellowed.

Answer 1

soapy water and a toothbrush.