Diamond treatments refer to the processes done to alter the appearance of a diamond by enhancing one of the qualities of the stone, most commonly its clarity or color.
Types of diamond treatments
1. To improve clarity -This includes removal of inclusions through internal and external laser drilling and the filling of fractures.
a) External laser drilling
A laser beam drills a small hole into the inclusion and the stone is then acid cleaned to bleach out the inclusion. This treatment was introduced in the 1960s because of the advantage that it is more cost effective than re-polishing given that less weight is lost.
b) Internal laser drilling
This is a newer technique that treats inclusions that are located near the surface. A laser is used to heat an inclusion, creating stress that results in fractures extending to the surface, then the stone is acid cleaned to dissolve dark inclusions. The risk is that lasering can potentially fracture the stone.
An alternative method is that holes are drilled to link fissures that exist within the stone with those on the surface then the stone is acid cleaned to remove dark inclusions.
The laser drill hole from external laser drilling is visible on the surface. Once set in a piece of jewellery the drill hole is sometimes concealed making it more difficult to identify.
It is more difficult to detect internal laser drilling because no hole exists on the surface. There are some tell-tale signs however, including worm-like holes around irregular fractures.
-The treatment that has been done must be disclosed and also a description of the the treatment included.
-Gem laboratories issue grading certificates with all treated diamonds fully disclosed, and in the comments section the particular treatment must be specified.
-Additionally, descriptions that infer that the processes are a normal part of the polishing process or misleading to consumers cannot be used.
-Company names that contain the word diamond must also include the word treated.
c) Crack filling
This method uses a hot and pressured environment to force a liquid glass material to enter any fractures that appear on the surface of a stone. The glass used is highly refractive, like diamonds, therefore effectively disguises fractures.
A problem is that such treated diamonds are not as strong as diamonds and the treatment is not always permanent as the filler can deteriorate and discolor; acid cleaning can damage the filler; and the high temperatures used to work on settings can melt the glass.
Physical properties: red-purple-blue colors can be seen when looking from the pavilion end; air bubbles are present, as are color flashes; and sometimes filling can be found on the surface.
Tests: The appropriate test depends on the type of filler used. An X-ray radiographic technique is used to detect the presence of lead-based glass. Alternatively, a fluorescence X-ray test shows high contrast when heavy elements are used in the filler.
The treatment must be disclosed at point of sale. Gem laboratories will not provide certificates of stones which have had cracks filled.
2. To improve color -The color of a diamond is created by impurities present within the lattice structure of the diamond, in particular the presence of nitrogen and boron. These impurities cause certain wavelengths of color to be absorbed leading to color being reflected.
Depending on the type and amount of impurity present in a diamond, results in the production of different colored diamonds. A classification system of diamond types has been developed based on these differences.
Type Ia: diamonds with groups of nitrogen atoms, results in diamonds with a color spectrum ranging from colorless to yellow. This type of diamond represents the majority of diamonds.
Type Ib: contain isolated nitrogen atoms, dispersed throughout the structure, which result in diamonds that are yellow, orange or brown in color.
Type IIa: contain little or no nitrogen, therefore the color ranges from colorless, yellow-brown, to pink and purple.
Type IIb: contain boron and results in blue-grey colored diamonds.
There are currently three treatments used to enhance the color of diamonds: irradiation; surface coating; and HPHT.
Whereby diamonds are treated with nuclear rays to alter the color of diamonds.
There are different types of irradiation technologies are available, including:
- Electron irradiated diamonds which cause diamonds to become greeny-blue.
-Neutron irradiated which leads to dark green colored diamonds and if over irradiated they turn black.
-Ion implantation which results in the color changing to a green or even a black surface.
-Irradiation and heat treatment which leads to further color change.
Changes after irradiation and heat treatment:
Type Ia diamonds turn a brown or orange-brown color.
Type Ib diamonds turn purple.
Type IIa turn brown.
Type IIb return to their original color.
Physical properties: patchy color concentration; distinct color zoning; corrosion pits; black diamonds with green cracks; radioactivity in inclusions; and radiation stains.
Tests: Spectroscopic tests are used to test for electron irradiated diamonds. When neutron irradiated diamonds are illuminated from behind with intense white light a dark green color can be seen.
b) Surface coating
This is the oldest treatment done to diamonds, whereby a stone is covered with another material to change the color of the stone. Materials originally used included foils or varnishes. The aim of treatments is often to neutralize a stone’s color, for example applying a blue coating to a yellow stone results in a colorless looking stone. The treatments only affect the surface and are only temporary.
Newer diamond-like surface coatings have been invented such as Physical Vapour Deposition (PVD) and Chemical Vapor Deposition (CVD). It would not be of benefit to add such materials to polished diamonds as rather than improve the color they create a grayish tint. It would be possible to apply such materials to simulants, however a thermal test could detect a stimulant stone given the thinness of the added layer.
c) HPHT: High Pressure High Temperature treatment
This treatment involves heating a diamond at a very high temperature under very high pressure, which leads to the composition of the diamond to be restructured whereby defects are reorganized and color is improved.
This process transforms Type IIa diamonds to almost colorless and type Ia from brown to a yellow or green-yellow color.
Physical properties: green fluorescence; strong grains; crack cleavage under the table; corrosion marks; and blackish cracks.
Tests: Spectroscopic tests can be used for detecting HPHT treated diamonds. In particular the photoluminescence spectroscopy test is appropriate for testing type IIa HPHT treated diamonds.
All HPHT treated stones must be disclosed as HPHT treated diamonds to consumers .
Products that imitate the appearance of some characteristics of diamonds. But they do not have the same structural or physical composition as diamonds.
Types of simulants
1. Cubic zirconia is the most common stimulant and has been readily available in jewelery since the 1970s. This became used in jewellery because of the very low cost of production due to easy manufacturing methods and structure does not contain any impurities or inclusions, and is therefore very sparkly and clear.
2. Moissanite is very rarely found in nature, but a synthetic form is being produced. This type of diamond simulant is much newer, only available on the market since the late 1990s. Synthetic moissanite can be found to range from near colourless, to yellow and dark green.
Physical differences: It has a different appearance to a diamond, it can have a hazy or milky appearance depending on quality; a thicker girdle; and because it is not as hard as diamond it can have external damages.
Tests: The following tests can be conducted- a gravity test; a gem print whereby cubic zirconia relects light differently to diamonds; and a heat conductivity test, whereby cubic zirconia will register red as opposed to diamonds which register green.
Physical differences: It has different features to diamonds, including long white inclusions; a double internal reflection of where facets meet; and the girdle can be made twice which can lead to uneven shapes.
Tests: Thermal testing is not reliable for testing synthetic moissanite as it cannot differentiate between diamond and moissanite. Appropriate detection tests include optical transmission; electrical conductivity; and infrared.
Both simulants are generally fully disclosed and marketed under their own names. If manufacturers and retailers want to include the word diamond in reference to products made from simulants, then they must use it in conjunction with a descriptor such as simulant, fake, or imitation. Similarly, the name of the manufacturer or retailer can not only have the word diamond in it, it must also be accompanied by a qualifying term such as stimulant, fake, imitation.
These are stones that have been partly or entirely crystallized or re-crystallized in a laboratory, and with the exception of being man-made, the stone has the same physical and chemical structure as diamonds.
Types of Synthetics
There are two types of synthetics High Pressure High Temperature (HPHT) and Chemical Vapor Deposition (CVD).
1. HPHT: this type of synthetic is produced by subjecting a piece of graphite to extreme pressure and heat resulting in a stone being produced that is up to one carat in size and the equivalent of SI clarity. The color of stones produced through this technique are generally yellow-orange and yellow-brown and very rarely nearly colorless.
2. CVD: a combination of methane and hydrogen gases are subjected to an existing polished natural diamond, in an environment heated and below normal pressure resulting in the gaseous vapor condensing on the surface of the natural diamond to form a larger synthetic. Synthetics produced by
CVD techniques range from near colorless to brown.
Physical characteristics: different crystal growth patterns and presence of a seed crystal; hourglass shaped grains; color zoning; lots of inclusions; multiple growth faces of HPHT synthetics leads to a cube-octahedral shaped as opposed to an octahedral shape of natural diamonds. CVD produced synthetics are tabular or block shaped; fluorescent; clouds of white particles located along a plane.
Under a microscope: synthetics have lots of inclusions; inclusions located on the girdle; fractures; black spots can be seen in HPHT synthetics as the result of overheating that has lead to graphite fracturing.
- Spectroscopic tests such as infrared and UV.
- Cathode luminescence shows cross
-like growth sectors in HPHT synthetics.
-Strain patterns are visible under polarized light.
- HPHT phosphorescence (after glow) once ultraviolet lamps are turned off.
- Fluorescence patterns differ to patterns in natural diamonds. Yellow-green fluorescence in a yellow stone indicates that it is a HPHT synthetic; whereas red fluorescence in a brown or colorless stone highlights that it is a CVD synthetic.
- Magnetic tests find that synthetics can be moved by a powerful magnet whereas diamonds cannot.
- A synthetic must always be disclosed. The use of the word ‘diamond’ can only be used in conjunction with the term synthetic; man-made or artificial.
-Misleading descriptors of synthetics such as ‘cultured’ cannot be used.
- Firms that deal in synthetics can only use terms as listed above in their name.
-Gemological laboratories produce reports for synthetics with the synthetic nature of the diamond fully disclosed.
DiamondClub does not trade in synthetics. Our suppliers are diamond mining/polishing companies (DTC Sight Holders, De Beers, ALROSA, BHP Billiton, Rio Tinto, Peltra Diamonds, Consortium) and reputable suppliers that do not trade in synthetics. Furthermore, we do not sell to companies that trade in synthetics. Also our diamonds come with GIA’s Grading Report which all stones are screened to determine if it is synthetic.
A GIA grading report provides an expert analysis of a diamond’s quality based upon the “4Cs” of diamond grading: carat, color, cut and clarity. The GIA Diamond Grading Report also contains a plotting diagram that clearly shows a diamond’s unique inclusions and other clarity characteristics. It undergoes a technical screening process, determining its potential as a synthetic or diamond stimulant, and is tested to ensure that the color is natural. Because GIA is not affiliated with any commercial enterprise, impartial and accurate analysis of a diamond’s quality and value is assured
DiamondClub’s employees are trained to detect synthetics so they can detect if synthetics have fraudulently been included in parcels.