Tables for
Volume D
Physical properties of crystals
Edited by A. Authier

International Tables for Crystallography (2006). Vol. D, ch. 1.4, p. 100


H. Küppersa*

aInstitut für Geowissenshaften, Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
Correspondence e-mail:

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Shape of the quadric and symmetry restrictions

SystemQuadricNo. of independent componentsNonzero components
ShapeDirection of principal axes
Triclinic General ellipsoid or hyperboloid No restrictions 6 [Scheme scheme1]
Monoclinic One axis parallel to twofold axis (b) 4 [Scheme scheme2]
Orthorhombic Parallel to crystallographic axes 3 [Scheme scheme3]
Trigonal, tetragonal, hexagonal Revolution ellipsoid or hyperboloid c axis is revolution axis 2 [Scheme scheme4]
Cubic, isotropic media Sphere Arbitrary, not defined 1 [Scheme scheme5]