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.
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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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