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Glittering
Stones >> Crystal
Glittering Stones Crystal
A crystal
is a solid  in
which the element atoms, molecules, or at times ions are packed
in a regularly ordered, repeating pattern expanding in all three
spatial dimensions.
Crystalline structures arise in all classes
of materials, with all types of chemical bonds. Almost all metal
exists in a polycrystalline state; amorphous or single-crystal
metals should be formed synthetically, frequently with
great difficulty. Ironically bonded crystals
could form upon solidification of salts, either from a dissolves
fluid or when it condenses from a solution. Covalently
bonded crystals are also extremely common, notable examples
being diamond,
silica, and graphite. Polymer materials usually would form crystalline
regions, but the lengths of molecules usually prevent total crystallization.
Historical Facts of Crystal
| Crystal
Density |
| Group I |
Group II |
Group III |
| < 1 g.cm-3 |
1 - 1.2 g.cm-3 |
> 1.2 g.cm-3 |
|
| Mohs
Scale Hardness |
| Diamond |
Sapphire |
Gypsum |
Calcite |
Apatite |
Orthoclase |
Boron Carbide |
Cubic Boron Nitride |
| 10 |
9 |
2.5 |
3.5 |
5.5 |
6.5 |
9.5 |
9.9 |
|
| Types
Of Crystal |
| Covalent Crystals |
Metallic Crystals |
Ionic Crystals |
Molecular Crystals |
|
| Crystal System |
| Triclinic |
Monoclinic |
Orthorhombic |
Tetragonal |
Trigonal |
Hexagonal |
Cubic |
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Gem Jewelry of Crystal
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