Table 3.3.6.2

Hahn, Th.; Klapper, H.

doi:10.1107/97809553602060000644

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

pdf | chapter contents | chapter index | related articles

International Tables for Crystallography (2006). Vol. D. ch. 3.3, p. 404

Table 3.3.6.2

Th. Hahn^a ^* and H. Klapper^b

^a Institut für Kristallographie, Rheinisch–Westfälische Technische Hochschule, D-52056 Aachen, Germany, and ^bMineralogisch-Petrologisches Institut, Universität Bonn, D-53113 Bonn, Germany
Correspondence e-mail: hahn@xtal.rwth-aachen.de

Table 3.3.6.2 | top | pdf |
Gypsum: cosets of alternative twin operations of the dovetail and the Montmartre twins, referred to their specific orthorhombic axes (subscripts D and M)

$[{\cal H}]$	Dovetail twins $[m_{x{\rm D}} \times {\cal H}]$	Montmartre twins $[m_{z{\rm M}} \times {\cal H}]$
1	$[m_{x{\rm D}} = m \parallel(100) ]$ (rational)	$[m_{z{\rm M}} = m\parallel (001) ]$ (rational)
$[2_y = 2 \parallel [010]]$	$[m_{z{\rm D}} = m\perp[001]]$ (irrational)	$[m_{x{\rm M}} = m\perp[100]]$ (irrational)
$[m_y = m \parallel (010)]$	$[2_{z{\rm D}} = 2\parallel[001] ]$ (rational)	$[2_{x{\rm M}} = 2\parallel [100]]$ (rational)
$[{\bar 1}]$	$[ 2_{x{\rm D}} = 2\perp(100)]$ (irrational)	$[2_{z{\rm M}} = 2\perp[001]]$ (irrational)