Crystal Structure of Typical Snow Crystals of Low Temperature Types

Noboru Sato, Katsuhiro Kikuchi
1989 Journal of the Meteorological Society of Japan  
The correlation among the gohei twins, seagull and spearhead-type crystals, which are typical polycrystalline snow crystals of low temperature types, was discussed based on a number of microphotographs taken in the polar regions and obtained in laboratory experiments. The crystal structure of the spearhead type was determined, that is, the angle between the c-axes is 116* and the supplementary angle of intersection of two prism planes is 31*. The spearhead-type crystal is the twin whose
more » ... plane is {1013}, and corresponds to the gohei twin whose tip angle is 54*. It is one wing of the seagull-type crystals of the inside bend from the center. The other wing of the seagull-type crystals of the inside bend from the center grows from the boundary of the mother crystal of the spearhead-type crystal, and has the same crystal structure as the mother crystal. There is another snow crystal of the seagull-type, the seagull type of the outside bend from the center, which has an angle between two wings of about 130*. The structure of their wings is the same as the spearhead-type snow crystals. This may be a penetration twin of the spearhead-type snow crystals. The formation mechanisms of gohei twins and spearhead crystals are considered based on a cubic structure model and the rotation of an ice crystal lattice about <0001> axis on the basal face. 522
doi:10.2151/jmsj1965.67.4_521 fatcat:payvugcgvvdmvl7vpv26dkfrby