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Fascinating facts about crystals
Three illustrated crystals are shown to demonstrate different crystal classes and symmetries: a tall, prismatic monoclinic gypsum crystal; a pointed, double-ended tetragonal wulfenite crystal; and a cubic isometric halite crystal, each labeled with its crystal class and symmetry content. Diagram showing the seven primitive crystal systems with labeled 3D shapes: isometric (cubic), tetragonal, orthorhombic, hexagonal, triclinic, monoclinic, and rhombohedral (trigonal), each with axis orientation and a brief description of their geometric properties.
Animated snowflake against a dark background.
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crystallography

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Fascinating facts about crystals
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Fascinating facts about crystalsDiscover five facts about crystals.
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Three illustrated crystals are shown to demonstrate different crystal classes and symmetries: a tall, prismatic monoclinic gypsum crystal; a pointed, double-ended tetragonal wulfenite crystal; and a cubic isometric halite crystal, each labeled with its crystal class and symmetry content.
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examples of well-shaped crystalsEach of these examples of well-shaped crystals belongs to a different crystal class because of its overall symmetry content.

crystallography, branch of science that deals with discerning the arrangement and bonding of atoms in crystalline solids and with the geometric structure of crystal lattices. Classically, the optical properties of crystals were of value in mineralogy and chemistry for the identification of substances. Modern crystallography is largely based on the analysis of the diffraction of X-rays by crystals acting as optical gratings. Using X-ray crystallography, chemists are able to determine the internal structures and bonding arrangements of minerals and molecules, including the structures of large complex molecules, such as proteins and DNA.

The Editors of Encyclopaedia Britannica This article was most recently revised and updated by John P. Rafferty.