Monoclinic crystal system Information & Monoclinic crystal system Links at HealthHaven.com

An example of the monoclinic crystals, orthoclase

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°.

[edit] 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.

Simple monoclinic (P)

Centered monoclinic (C)

[edit] Crystal Classes

The monoclinic crystal system class names, examples, Schönflies notation, Hermann-Mauguin notation, point groups, International Tables for Crystallography space group number^[1], orbifold, type, and space groups are listed in the table below.

Crystal Class

Example

Schönflies

Hermann-Mauguin notation

point groups

#

orbifold

Type

space groups

Sphenoidal ^[2]

halotrichite

C₂

$2\$

3-5

22

enantiomorphic polar

$\mathrm{P}2\,\!$

$\mathrm{P}2_{1}\,\!$

$\mathrm{C}2\,\!$

Domatic ^[2]

hilgardite

C_1h (=C_1v = C_s)

m

$\bar{2} = m$

6-9

1*

polar

$\mathrm{Pm}\,\!$

$\mathrm{Pc}\,\!$

$\mathrm{Cm}\,\!$

$\mathrm{Cc}\,\!$

Prismatic ^[2]

gypsum

C_2h

$2/m\,\!$

10-15

2*

centrosymmetric

$\mathrm{P}2/\mathrm{m}\,\!$

$\mathrm{P}2_{1}/\mathrm{m}\,\!$

$\mathrm{C}2/\mathrm{m}\,\!$

$\mathrm{P}2/\mathrm{c}\,\!$

$\mathrm{P}2_{1}/\mathrm{c}\,\!$

Typical crystal forms for the monoclinic-prismatic crystal class:
Wolframite, 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.

[edit] See also

Crystal structure

[edit] References

^ Prince, E., ed (2006). International Tables for Crystallography. International Union of Crystallography. doi:10.1107/97809553602060000001. ISBN 978-1-4020-4969-9.
^ ^a ^b ^c "The 32 crystal classes". http://www.cartage.org.lb/en/themes/sciences/physics/SolidStatePhysics/AtomicBonding/CrystalStructure/32Crystal/32Crystal.htm. Retrieved 2009-07-08.

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

[ITC-0] Prince, E., ed (2006). International Tables for Crystallography. International Union of Crystallography. doi:10.1107/97809553602060000001. ISBN 978-1-4020-4969-9.

[x-name-1] "The 32 crystal classes". http://www.cartage.org.lb/en/themes/sciences/physics/SolidStatePhysics/AtomicBonding/CrystalStructure/32Crystal/32Crystal.htm. Retrieved 2009-07-08.

[1]

[2]

Contents

[edit] Bravais lattices and point/space groups

[edit] Crystal Classes

[edit] See also

[edit] References