day 8 of 14 day water fast. surprise bowel motion and curious objects in stool.

i did a Liver Flush just before the fast (6th one in the last 10 years) and as normal got rid of bunch of stones. i started the fast rite after my diarhea was over. figured the epsum salt flush had moved all the current food out of my intestines. now 2 days ago i felt a small urge for bowel movenent. so i went to toilet and forced a bit of stool out. when i examined it i found chunks of greyish white gritty stones, irregular in shape with more than 1/2 inch in diameter. they comprised about half of the stools. i could break them by pressing with a metal rod. any one knows what they could be or where they came from??
would appreciate any insight Tweet