Ice on a puddle? No, it's salt crystals I found this morning in the bottom of my sphaghetti pot. A little bit of salty water had dried up leaving these crystals behind. There's several interesting things about the image to me: it demonstrates very well the idea of domains - crystals started at various nucleation points and grew out and met each other. It's also interesting to see different growth behaviors in different parts of the pot, probably depending on drying rate and salt concentration. In some areas you have long linear crystals; in other areas the growth is more compact. Most of the crystals branch at 90 degree angles, but a few grow in a more spidery pattern. (Somewhat reminiscent of patterns you get in diffusion limited aggregation simulations.)