Most of my Gallstones were all under a centimeter in size.
Although I did flush one about 1 inch long by a half of and inch wide, I was amazed to see this one come out. The ones on the ultrasound only showed about a dozen gallstones, all being about a centimeter or smaller. I think maybe this one was stuck in a bile duct, because of the shape. It was totally tubular looking...to the max.
I did get a few tan ones out, those ones seemed more hard. Most of them are green and they have dark green crystals inside of them. I totally flushed 183 all together. This has been after 7 flushes.
How many flushes have you done?
Some people on this site are using Gold Coin Grass to help break up the larger stones.
You may want to try some different flush recipes, also.