Why rock in fridge cloudiness?

Curious children will realize that transparent water sometimes creates oddly chiseled stones. The main reason is that the clear water you pour into the ice tray is not completely pure, but contains a small amount of mineral and suspended solids.

Since all objects are frozen from the outside, the center of the rock will be the last to be solidified. The water contains no residue and minerals freeze first, pushing the chisel containing residue (and even small bubbles) into the center. The result is a harmless chisel of ice.

The lumps are not only chiseled in the refrigerator, but they also shrink significantly after about 1-2 weeks due to sublimation - the term used for direct evaporation from the solid phase to the gas phase.

T. An