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Monoclinic crystal system

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]] In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a parallelogram as its base. Hence two pairs of vectors are perpendicular, while the third pair makes an angle other than 90°.

Bravais lattices and point/space groups

Two monoclinic Bravais lattices exist: the simple monoclinic and the centered monoclinic lattices, with layers with a rectangular and rhombic lattice, respectively.

image:Monoclinic.svg|Simple monoclinic (P) image:Monoclinic-base-centered.svg|Centered monoclinic (C)

Crystal Classes

The monoclinic crystal system class names, examples, Schönflies notation, Hermann-Mauguin notation, point groups, International Tables for Crystallography space group number, orbifold, type, and space groups are listed in the table below.

{| align=center |----- align=center | bgcolor=#ffffc0 | Crystal Class | bgcolor=#c0ffff | Example | bgcolor=#ffff00 | Schönflies | bgcolor=#c0ff00 | Hermann-Mauguin notation | bgcolor=#c0ffff | point groups | bgcolor=#a0ff80 | # | orbifold | Type | bgcolor=#ffffc0 colspan=8| space groups

|----- valign=top | monoclinic | bgcolor=#c0ffff | halotrichite | bgcolor=#ffff00 | C₂ | bgcolor=#c0ff00 | $2$ | bgcolor=#c0ffff | $2$ | bgcolor=#a0ff80 |3-5 | 22 |enantiomorphic polar | bgcolor=#ffffc0 | $mathrm\{P\}2,!$ || $mathrm\{P\}2\_\{1\},!$ || $mathrm\{C\}2,!$

|----- valign=top | Domatic | bgcolor=#c0ffff | hilgardite | bgcolor=#ffff00 | C_1h (=C_1v = C_s) | bgcolor=#c0ff00 | $m$ | bgcolor=#c0ffff | $bar\{2\}\; =\; m$ | bgcolor=#a0ff80 |6-9 | 1* | polar | bgcolor=#ffffc0 | $mathrm\{Pm\},!$ || $mathrm\{Pc\},!$ || $mathrm\{Cm\},!$ || $mathrm\{Cc\},!$

|----- valign=top | Prismatic | bgcolor=#c0ffff | gypsum | bgcolor=#ffff00 | C_2h | bgcolor=#c0ff00 | $2/m,!$ | bgcolor=#c0ffff | $2/m,!$ | bgcolor=#a0ff80 |10-15 | 2* | centrosymmetric | bgcolor=#ffffc0 | $mathrm\{P\}2/mathrm\{m\},!$ || $mathrm\{P\}2\_\{1\}/mathrm\{m\},!$ || $mathrm\{C\}2/mathrm\{m\},!$ || $mathrm\{P\}2/mathrm\{c\},!$ || $mathrm\{P\}2\_\{1\}/mathrm\{c\},!$ || $mathrm\{C\}2/mathrm\{c\},!$

|}

, Gypsum, Sphene, Augite and Orthoclase]]

Sphenoidal is also monoclinic hemimorphic; Domatic is also monoclinic hemihedral; Prismatic is also monoclinic normal.

The three monoclinic hemimorphic space groups are as follows:

• a prism with as cross-section wallpaper group p2
• ditto with screw axes instead of axes
• ditto with screw axes as well as axes, parallel, in between; in this case an additional translation vector is one half of a translation vector in the base plane plus one half of a perpendicular vector between the base planes

The four monoclinic hemihedral space groups include

• those with pure reflection at the base of the prism and halfway
• those with glide planes instead of pure reflection planes; the glide is one half of a translation vector in the base plane
• those with both in between each other; in this case an additional translation vector is this glide plus one half of a perpendicular vector between the base planes.

See also

• Crystal structure

References

• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., pp. 65 - 69, ISBN 0-471-80580-7

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