My remembrances of my grandmother showing me chicken gizzards and gizzard
stones was like Dwayne James'.  As I recall, the gizzards were filled with
small to large pieces of sand.  That's why I wondered about the 1 cm size
reported by Dan Mouer.  I pity Eugene R. Prince's cat, if there are any
shrieks at night it may not be because the cat's in heat.  ;-)
 
Tom Wheaton