What are ice crystals?

Ice crystals are defined as unbranched ice crystals that can take the form of needles and plates. This characteristic is significant in meteorology, as it describes the specific physical structures and forms ice can exhibit when it forms in the atmosphere, particularly at higher altitudes and colder temperatures. Ice crystals are generally a product of sublimation, where water vapor turns directly into solid ice without becoming liquid first.

In contrast, small balls of ice typically refer to hail or sleet, which are different phenomena. Liquid drops greater than 0.5 mm pertain to larger raindrops and are not frozen. White grains of ice can be misleading, as they could refer to snow or granular ice forms, which are not specifically classified as ice crystals. Therefore, the definition of ice crystals being unbranched structures made up of needles and plates is the most accurate and relevant within the context of weather phenomena and observations.