I had a sprain in my leg a few days back. The doctor recommended dipping my foot alternately in ice-cold and hot water to aid blood circulation. It is here that I discovered something interesting.
The picture above shows the piece of ice that was put in the bucket. The above picture shows the ice cube from above.
If you look at the large piece of cube from the side (see below), you can see that the upper part of the cube, that was near the open surface of the container in which the ice froze, seems to be almost transparent and has a crystalline appearance. The lower part does not have this appearance, and it is white and opaque.
Why is there a difference in the layers of ice in the large cube? Is it because the water was from tap and not completely pure? The water was put in the refrigerator for a period greater than 12 hours, so the ice has frozen properly. Can anyone explain this unique structure of ice? I've never seen this before.
This update is to simply demonstrate the bubble formation in the ice,which causes the cloudiness. Out of the two answers, I had accepted the one by @IliaSmilga . Today, the ice formed demonstrated this idea clearly. Given below are the pictures in which the bubbles of dissolved gas are clearly visible.
The last two pictures are the best.