Ice crystals may form late in the day under clear skies and light winds as the temperature drops and fall as soft showers. As they flutter slowly downward, they may glitter in sun or moon light and thus earn the name diamond dust . The latter resemble stubby pencils rather than the delicate branched snowflake shape. When their diameter is less than 15-20 micrometres, crystal plates tumble randomly through the air as they fall. But when the plates are larger, they fall so that their long dimension parallels the ground, floating downward like descending flying saucers.
Ice needles are special varieties of snow or ice crystals.
Ice needle snow may produce high danger of avalanche when falling in mountain areas. They are formed by the re-freezing of rain or drizzle drops or partially melted snowflakes falling through a cold air layer near the surface. Often called sleet in United States, they bounce when hitting a hard surface. Graupel , Snow Pellets or Soft Hail are soft, opaque ice particles, irregular in shape and often studded with oblong or branched protrusions. Graupel splatters when it impacts onto a surface.