APPENDIX 2

The 47 Possible Forms Distributed Among the Different Crystal Systems1

CrystalClass

SymmetryElements2

Forms Occurring in theRespective Crystal Class

Representative Inorganic/Mineral Substances

Triclinic1 E Pedion Ca8B18Cl4 . 4H2O1̄ E, i Pinacoid MnSiO3

Monoclinic

2 E, C2 Sphenoid, pedion, pinacoid FeAl2(SO4)4 . 22H2Om E, sh Sphenoid, pedion, pinacoid CaMg(AsO4)F2/m E, C2, I, sh Prism, pinacoid As2S3

Orthorhombic

222 E, C2, C02, C02 Disphenoid, prism, pinacoid ZnSO4 . 7H2Omm2 E, C2, sv, sv Pyramid, prism, dome, pinacoid,

pedionBaAl2Si3O10 . 2H2O

mmm E, C2, C02, C02sv,sv, sh

Dipyramid, prism, pinacoid Sulfur

(Continued)

Principles of Inorganic Materials Design, Second Edition. By John N. Lalena and David A. ClearyCopyright # 2010 John Wiley & Sons, Inc.

565

CrystalClass

SymmetryElements2

Forms Occurring in theRespective Crystal Class

Representative Inorganic/Mineral Substances

Tetragonal

4 E, 2C4, C2 Tetragonal pyramid, tetragonalprism, pedion

None known

4̄ E, 2S4, C2 Tetragonal disphenoid, tetragonalprism, pinacoid

Ca2B(OH)4AsO4

4/m E, 2C4, C2, i, 2S4,sh

Tetragonal dipyramid, tetragonalprism, pinacoid

PbMoO4

422 E, 2C4, C2, 2C02,2C200

Tetragonal trapezohedron,tetragonal dipyramid,ditetragonal prism,tetragonal prism, pinacoid

Pb2CO3Cl2

4mm E, 2C4, C2, 2sv,2sd

Ditetragonal pyramid, tetragonalpyramid, ditetragonal prism,tetragonal prism, pedion

Pb2Cu(OH)4Cl2

4̄2m E, C2, 2C02, 2sd, 2S4 Tetragonal scalenohedron,tetragonal disphenoid,tetragonal bipyramid,ditetragonal prism, tetragonalprism, pinacoid

Cu2FeSnS4

4/mmm E, 2C4, C2, 2C02,2C002, i, 2S4, sh,2sv, 2sd

Ditetragonal dipyramid,tetragonal dipyramid,ditetragonal prism, tetragonalprism, pinacoid

Rutile

Trigonal (Rhombohedral)

3 E, 2C3 Trigonal pyramid NaIO4 . 3H2O3̄ E, 2C3, i, 2S6 Rhombohedron, hexagonal

prism, pinacoidFeTiO3

32 E, 2C3, 3C02 Trigonal trapezohedron,rhombohedron, trigonaldipyramid, ditrigonal prism,hexagonal prism, trigonal prism,pinacoid

Low quartz

3m E, 2C3, 3sv Ditrigonal pyramid, trigonalpyramid, hexagonal pyramid,ditrigonal prism, trigonal prism,hexagonal prism, pedion

KBrO3

3̄m E, 2C3, 3C02, Hexagonal scalenohedron,rhombohedron, hexagonaldipyramid, dihexagonalprism, hexagonal prism,pinacoid

Corundum

(Continued)

APPENDIX 2566

CrystalClass

SymmetryElements2

Forms Occurring in theRespective Crystal Class

Representative Inorganic/Mineral Substances

Hexagonal

6 E, 2C6, 2C3, C2 Hexagonal prism, pedion Nepheline6̄ E, 2C6, sh, 2S3 Trigonal dipyramid, trigonal

prism, pinacoidNone

6/m E, 2C6, 2C3, C2, i,2S3, 2S6, sh

Hexagonal dipyramid, hexagonalprism, pinacoid

Apatite

622 E, 2C6, 2C3, C2,3C02, 3C002

Hexagonal trapezohedron,hexagonal dipyramid,dihexagonal prism, hexagonalprism, pedion

High quartz

6mmm E, 2C6, 2C3, C2,3sv, 3sd

Dihexagonal pyramid, hexagonalpyramid, dihexagonal prism,hexagonal prism, pedion

Wurtzite

6̄m2 E, 2C3, 3C02, sh,2S3, 3sv,

Ditrigonal dipyramid, trigonaldipyramid, hexagonaldipyramid, ditrigonal prism,hexagonal prism, trigonal prism,pinacoid

BaTiSi3O9

6/mmm E, 2C6, 2C3, C2,3C02, 3C002 i, 2S3,2S6, sh, 3sv, 3sd

Dihexagonal dipyramid,hexagonal dipyramid,dihexagonal prism, hexagonalprism, pinacoid

Beryl

Cubic

23 E, 8C3, 3C2 Tetartoid, deltohedron,tristetrahedron, pyritohedron,tetrahedron, dodecahedron, cube

NaBrO3

m3 E, 8C3, 3C2, i, 8S6,3sh

Diploid, trisoctahedron,trapezohedron, pyritohedron,octahedron, dodecahedron, cube

Pyrite

432 E, 8C3, 3C2, 6C2,6C4

Gyroid, trisoctahedron,trapezohedron, tetrahexahedron,octahedron, dodecahedron, cube

None

4̄ 3m E, 8C3, 3C2, 6sd,6S4

Hextetrahedron, deltohedron,tristetrahedron, tetrahexahedron,tetrahedron, dodecahedron, cube

Sphalerite

m3m E, 8C3, 3C2, 6C2,6C4, 6sd, i, 8S6,3sh, 3sh, 6S4

Hexoctahedron, trisoctahedron,trapezohedron, tetrahexahedron,octahedron, dodecahedron, cube

Diamond

1See, Buerger, M. Elementary Crystallography, MIT Press, 1978, pp. 112–168.2E ¼ identity element, i ¼ inversion center, Cn ¼ n-fold proper rotation axis, Sn ¼ n-fold improper rotation(rotoreflection) axis, sv ¼ vertical mirror plane (reflection plane contains principal axis), sh ¼ horizontalmirror plane (reflection plane ? to principal axis), sd ¼ diagonal mirror plane (reflection plane containsprincipal axis and bisects the angle between the two-fold axes normal to the principal axis).

APPENDIX 2 567