Water is complicated stuff! There are at least sixteen known crystal phases of ice, many shown here. For example, if you take ordinary ice - called ice Ih, because it's hexagonal - and cool it below -37 °C, it will gradually turn into a cubic form, called ice Ic. In this form of ice the water molecules are arranged like carbons in a diamond! And apparently some of it can be found in ice crystals in the stratosphere.

But if you wait longer, ice below -37 °C will turn into ice XI. The transformation process is slow, but ice XI has been found in Antarctic ice that's 100 to 10,000 years old. This ice is ferroelectric, meaning that it spontaneously become electrically polarized, just like a ferromagnetic spontaneously magnetizes.
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