These were photographed in Vermont, but similar forms are common in fine, powdery snow in Alaska. The first photo I ever saw of these, in a very old children's book, described them as rare cufflink crystals, from a great storm that struck New England. Like wolves, they may be rare in New England, but not in Alaska. They are, however, very small. A sixteenth of an inch across is a large one, and that would hardly make a sizable cufflink for a Lilliputian.
Ice crystals are basically hexagonal prisms, like a section of pencil cut square on both ends.
Their mode of growth is controlled by moisture and temperature. At low humidities, the faces of a crystal grow fairly evenly. As the humidity rises, first the edges and then the corners begin to grow faster than the rest of the crystal. Temperature controls whether the crystal grows lengthwise, making a shape like a long pencil, or sideways, making a flat, hexagonal plate. At temperatures from 15 degrees F to -10 degrees F , the plate form dominates.