Acta Crystallographica Section A

Foundations of Crystallography

Volume 58, Part 4 (July 2002)


research papers



Acta Cryst. (2002). A58, 334-345    [ doi:10.1107/S0108767302005196 ]

Morphological possibilities in general crystallography. Snow crystals

A. Janner

Abstract: Morphological features of snow crystals are analyzed on the basis of concepts of a general crystallography, where point groups of infinite order are possible. The observations are first formulated in a set of rules, leading to a macroscopic growth lattice and to continuous growth boundaries. Both are brought in connection with two-dimensional integral invertible transformations. Families of boundaries are considered, labeled by a set of indices restricted by selection rules and generalizing the law of rational indices. These properties are indicated graphically on a sample of 12 natural snow crystals. Their geometric and arithmetic properties are summarized in a table.

Keywords: morphology; snow crystals.

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