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Diamond
Diamond is a solid form of carbon with a diamond cubic crystal structure. The name of the mineral has been known in Russian since the 15th century that is derived from the Turkic and Iranian-speaking peoples (Turkish "elmas", Arabic "لماس", Persian "الماس"), where it came from the ancient Greek "ἀδάμας" - "indestructible, irresistible".
Chemistry: С;
Crystal system: Cubic, hexoctahedral crystal class (point symmetry group);
Color: Typically colorless, with yellow, brown and gray hues, black. Less often brown, purple, pink, red, orange, yellow, green, blue, blue. Very rare varieties with the effect of color change.
Color is due to the structural defects in the diamond lattice, including macroscopic phases called inclusions (nitrogen, hydrogen, boron, aluminum, etc.).
Identification properties
| Physical properties | |
|---|---|
| Mohs hardness: | 10 |
| Density: | 3.50-3.52 g/cm3 |
| Cleavage: | Perfect on (111) |
| Fracture: | conchoidal |
| Optical properties | |
|---|---|
| Optical character: | isotropic, sometimes anomalous anisotropic |
| Refractive Index: | 2.417 – 2.421 |
| Birefringence: | none, anomalous – up to 0.002 |
| Pleochroism: | none |
| Dispertion: | 0.044(BG) |
| Luster: | Adamantine |
Inclusions and structural inhomogeneities
Mineral inclusions
In crystal inclusions
Zoning and structural inhomogeneities
Structural and optical anomaly
Gem basic treatments
| Treatment | Goal |
|---|---|
| High temperature | Altering the gem visual color |
| High temperature treatment under high pressure technique | Altering the gem visual color or enhancing the properties |
| Irradiation treatment; irradiation treatment in combination with high-temperature treatment, as well as under high-pressure | Altering the gem visual color |
| Impregnation with high-refractive agents to fill the open cavities | Improving the apparent clarity of gem material |
| Laser "drilling" to remove a dark inclusion with following tamping of the mouth of the drilling channel or without it | Improving the apparent clarity of gem material |
| Increasing the layer of synthetic diamond | Altering the gem visual color |
| Surface coating of cut diamond by applying a various coloring agent | Altering the gem visual color |
Inclusions and structural inhomogeneities
Crack filling
HPHT technique
Heat treatment
Irradiation followed by heat treatment
Drilling
Synthetic or Imitation gem materials
Methods of diamond manufacture for the jewelry industry:
- method of growing diamond crystals in flux at high temperature and high pressure (group of methods HPHT) technique;
- method of growing monocrystals and polycrystalline diamond aggregates from the gas phase (group of methods CVD).
The most commonly encountered synthetic diamond is as follows:
- zirconium oxide (or hafnium), stabilized in the crystalline state in cubic crystal system (fianit, dzhevalit, zirconite, CZ);
- colorless synthetic and natural spinel;
- synthetic garnets (YAG - yttrium-aluminum garnets, GGG - gallium-gadolinium garnets);
- synthetic moissanite;
- phianite or moissanite with diamond coating;
- doublets: diamond + topaz, diamond + corundum, diamond + glass, diamond + quartz;
- high refractive glasses (rhinestones).
Inclusions and structural inhomogeneities
HPHT-syntesis
Diamond Quality Factors
Most gemological characteristics of diamonds are based on single values for each of the four Cs:
- The carat weight measures the mass of a diamond. The mass of diamonds in jewelry can be defined by the calculation method;
- Color (in accordance with the standards of color of diamonds), defined in standard viewing conditions;
- The clarity of the diamond defined in accordance with the standard factors when a diamond is viewed under 10x magnification;
- The cut of a diamond describes the manner in which a diamond has been shaped and polished from its beginning form as a rough stone to its final gem proportions.
As additional quality factors, the presence or absence of luminescence, as well as the selection (for products with several or more large stones) in shape, size, color, clarity, and cut quality are taken into account.
