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# Crystal forms.

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### Crystal forms.

1. 1. Crystal forms..
2. 2. Cube <ul><li>general symbol is (100) </li></ul><ul><li>Bounded by six similar faces, each parallel to two of the axes. </li></ul><ul><li>Each face is a square and interfacial angles are 90 degree. </li></ul><ul><li>The faces of the cube are parallel to the principal or axial planes of symmetry. </li></ul>
3. 3. Octahedron (111) <ul><li>Is composed of eight equilateral triangular faces, each of which intersects all three crystallographic axes equally. </li></ul><ul><li>Faces of the octahedron truncate symmetrically the corners of the cube.. </li></ul>
4. 4. Rhomb-dodecahedron (110) <ul><li>Composed of 12- rhomb shaped faces. </li></ul><ul><li>Each face intersects two of the crystallographic axes equally and is parallel to the third. </li></ul><ul><li>The faces of the dodecahedron truncate the edges of both the cube and octahedron. </li></ul>
5. 5. Tetrahexahedron (hk 0) <ul><li>Composed of 24 isosceles triangular faces, each of which intersects one axis at unity and the second at some multiple and is parallel to the third. </li></ul><ul><li>With respect to the inclination of their faces different variety of tetrahedrons observed. </li></ul><ul><li>Most common one is (210) </li></ul>
6. 6. Trapezohedron(hll) <ul><li>24 trapezium shaped faces. </li></ul><ul><li>Each of which intersect one of the crystallographic axes at unity and the other two at equal multiples. </li></ul><ul><li>Some having different angles of inclination. </li></ul><ul><li>Most common is (211) </li></ul><ul><li>Its also known as tetragon-trioctahedron. </li></ul>
7. 7. Trisoctahedron (hhl) <ul><li>Composed of 24 isosceles triangular faces. </li></ul><ul><li>Each of which intersects two of the crystallographic axes at unity and the third axis at some multiple. </li></ul><ul><li>Face of which have different inclinations but most common is (221) </li></ul><ul><li>Also known as trigon-trioctahedron </li></ul>
8. 8. Hexoctahedron (hkl) <ul><li>Composed of 48 triangular faces </li></ul><ul><li>Intersects all three crystallographic axes at different lengths. </li></ul><ul><li>Symbol is there for (321) </li></ul><ul><li>Parametres are 1 a1, 3 a2, and 3/2 a 3. </li></ul>
9. 9. Pyritohedron (hk0) <ul><li>Also called as pentagonal dodecahedron. </li></ul><ul><li>Consist of 12 faces. Each of which intersect one crystallographic axis at unity, second axis at some multiple of unity and parallel to the third. </li></ul><ul><li>It is a typical form with the common species, pyrite. </li></ul>
10. 10. Diploid <ul><li>Bounded by 24 similar faces. </li></ul><ul><li>Each meeting axes at unequal distances. </li></ul><ul><li>Its general symbol is (hkl) I.e. (eg. 321) </li></ul><ul><li>It’s also sometimes called dyakisdodeahedron. </li></ul>
11. 11. Tetrahedron <ul><li>Bounded by four equilateral triangular faces. </li></ul><ul><li>Each of which intersects all crystallographic axes at unit length. </li></ul><ul><li>The tetrahedral form can be considered as derived from the octahedron by omission of the alternate faces and the extension of the others. </li></ul>
12. 12. Tristetrahedron (trigon- tritetrahedron) <ul><li>Form bounded by twelve like triangular faces. </li></ul><ul><li>Each face of the tetrahedron has been raised to accommodate three others. </li></ul><ul><li>Each face cuts two axes at equal length and the third at a smaller length. </li></ul><ul><li>General symbol (hll) eg. (211) </li></ul>
13. 13. Deltoid- dodecahedron <ul><li>Also known as tetragon- tritetrahedron. </li></ul><ul><li>This is a 12-faced form in which three four-sided faces occur in place of one face of the tetrahedron. </li></ul><ul><li>Each faces cuts two axes at an equal length and a third at a greater length. (hhl) </li></ul><ul><li>Considered to be made up of the twelve faces of the trisoctahedron that occur in alternate octants. </li></ul>
14. 14. Hextetrahedron <ul><li>It has 24 faces. </li></ul><ul><li>Each face of tetrahedron has been raised to accommodate six others. </li></ul><ul><li>These corresponding to the faces of the alternate octants of the hexoctahedron. </li></ul><ul><li>General symbol is (hkl) </li></ul>