Bill Cook, Age 11, Of Boise, Ida., for his question:

Why do crystals grow in different shapes?

Crystals, of course, grow from particles of matter called atoms and molecules. Small as they are, these fragments of matter have definite shapes and sizes. All m01ecules of water are alike. All atoms of carbon are alike. The shape and size of the particles help to determine the shape of a crystallized solid. The temperature and the rate at which the crystal grows may modify its form.

Particles of a certain shape tend to assemb1e themselves in a pattern of their own.  If you toss a deck of playing cards onto a table, they tend to fall into a flat, two sided pattern. Tiny water molecules are far more comp1ex in shape. When they assemble in crystals of ice, they interlock themselves in an open lattice design. The quality of the ice also varies with the rate at which the particles form solid crystals.