Treatments in diamonds

TREATED DIAMONDS - HPHT, Irradiation, Laser Drilling Treatments in Diamonds Explained | Jewelfields

What is a treated diamond?

A natural diamond which is enhanced for its color, clarity and brilliance by several man made processes like HPHT, irradiation, fracture filling, laser drilling, etc., is a treated diamond.   

Now we know about the fully natural earth mined diamonds and diamonds which are natural but treated in any certain ways or can say them as enhanced diamonds; Here we will discuss about the later ones and the various treatments done on them. From times the researchers and technologists have been tweking with this beautiful gemstone of earth, now with time and improvements in technology new ways of sophisticated treatments to improve the appereance of a naturally occouring diamond are practiced for the trade.

Treated Diamonds

HPHT ( high pressure high temperature ) diamonds

The process developed in the year 1950 is to grow an immature diamond (diamonds which are not fully crystalllized) in a lab and by applying a certain amount of controlled pressure and temperature which mimics naturally necessary temperature and pressure the carbon needs to convert into a diamond deep within the earth.

HPHT is an irreversible process and is applicable for both premature and a developed diamond; in the former the embroyo carbon molecule transforms to a fully grown strong stone by HPHT making it worthwhile from rough form, also in a mature diamond sometimes the minor flaws which are in the form of undeveloped crystals turns into diamond crystals providing more even clarity and shine to the stone.

Color alteration of HPHT diamonds: Diamonds do usually comes with minor shades of yellow, brown or green which diminishes towards colorless by HPHT treatment or a fancy premature color present formerly in the stone can become complete after the treatment.

Always a good clarity diamond is selected to be enhanced by HPHT because diamonds with inner fractures tend to tear apart when subjected to extreme amount of pressure which is 900,000 pounds and heat around 1500 degree celsius per square inch, so a minor to moderate transformation only happens to an already developed diamond with HPHT by structuring the left over raw crystals to diamond but for a premature diamond the changes happens fully resulting a lab grown diamond.

The diamond treated is a natural diamond and the enhanancement is permenant in nature, so pioneer labs will certify it as natural diamond but will always mention in comments about the HPHT treatment the natural diamond has under went, stating it as a natural HPHT treated diamond. There are various ways to identify HPHT treatment, one is by reaction to UV waves which will be stronger with shorter wave UV insted of long-wave UV; other way is the formation of metal within the crystal will never happen if the diamond is natural so the presence of metal is the way to identify a HPHT diamond.

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Irradiated diamonds or Color treated diamonds

These are color modified diamonds by irradiation which is the cause for any color change that happens in a diamond either in the natural condition over a course of millenniums or done in a laboratory in very short period of time in few hours to months. It happens due to the exposure of a diamond to radioactive waves including alpha, gamma and beta rays which involve thumping the mobility of carbon atoms in the diamond.  The three mentioned rays are formed of electrones, protons and neutrons present in the cell of an atom are selectively bombarded on a diamond in a necular reactor to color treat the diamond with radition.

Naturally the alpha rays provides a slight change in the color of the stone form giving it a tint or light shade towards green remaining near the skin of the crystal, but the gamma and beta rays provides a more intense penetration and significant color change.

The discovery of the lab irradiation process is not new but dates back to a century and a quarter when in 1904 an english chemist 'Sir William Crookes' discovered that a diamond color is changed when exposed to radium salts; but with his experiments the color changes remained near the surface area and not penetrated within, also the stone became so radioactive that was not suitable to wear.

Annealing process: Post irradiation treatment the diamonds sometimes are red heated at certain specified temperatures to alter the color of diamonds further which is called annealing.

Methods of irradiation:

Out of four irradiation treatments electron bombardment is a common irradiation treatment done on diamonds where Van De Graaff generators are used for electron bombardments on diamonds producing green, blue-green or blue color and these stones if further heated to temperature in range of 500 - 900 degree celsius convert stones to pink, brown, yellow, orange etc. The color penetration by this process is not deeper than 1mm from the surface.

Cyclotroning is a least used method where proton and neutron bombardment using cyclotrons is done on the diamond producing green-blue and green color in the stone which just remains to the surface. This is very uncommon as done direction centric and as all stones vary in cut the side from where the diamond is cyclotroned will have deeper color like if done from top it will form a deeper color ring on the crown and if done from sideways the side will catch more color compared to opposite side. The stones if further annealed to 800 degrees will turn them yellow, yellow-brown or orangish-yellow.

Neutron bombardment via nuclear reactor is the most common irradiation treatment performed for color altering a diamond producing blue, green, greenish blue, gray or black diamonds which further if red heated to 500-900 degree celsius produces fancy pink, yellow, orange, dark brown colors. Color is holistically penetrated in the stone from similar to what the gamma rays does.

Gamma ray bombardment by exposure to cobalt-60 is a cheapest way of color treating diamonds but is seldom used due to the long duration of few months it takes to color change the stones, mostly yellow tone stones are used in this and the result comes as blue or blue-green which is fully penetrated in the stone and these diamonds are not further annealed. The diamonds which have any tint of blue will post treatment get a greenish tint.

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What are laser drilled diamonds?

It is a treatment to remove an inner trapped inclusion in a diamond like foreign crystals, black carbon etcetera by drilling a microscopic whole through the surface to the inclusion site making a passage way, then the stone is boiled in some chemicals to melt the inclusion or even the inclusion is burnt by laser sometimes to improve the clarity of the diamond.

A diamond without any eye appearing inclusions are rarely found so the people in trade must always be wanting to find ways to remove inclusions from the diamonds and this is an easy and commonly adopted method for removing unwanted inclusions like lines or pin point naticals from a diamond. Sometimes a very good stone may just have a single ugly unaccepted inclusion so its a good accepted way to drill out the isolated inclusion by the method making the stone look more flawless.

The drill made by the laser just 20 microns in diameter that it is even much thinner to a human hair strand. There is then an another way to laser drilling which is uncommon where insted of laser burning the channel to the inclusion site, a micro plane is burned across the diamond untill it reaches the inclusion but the hollow space created this way is thicker then the laser drill but is more natural looking and not easily observable.

The laser holes are tough to be deducted by naked eyes so a microscope or a eye glaas can be used for it. Laser is a permanent treatment on a natural diamond and thus the laboratories like GIA (gemological institute of America) will mention the treatment as 'laser drilled' on a natural diamond report. If the diamond has any filling used similar to glass resin, then the GIA, American gem society will not certify those stones as the fracture filling is not permanent process and just by boiling the diamond will again come in the pre treated state.

A single drill will not affect the strength of the stone but if there are multiple drills in a single diamond will alter the bonding of the stone making it vulnerable; those stones falling in category of fracture filled diamonds are generally weak because of having hollow spaces within.

Treated Diamond Price

The price of these diamonds can remain slightly to significantly low on basis of treatment applied and its intensity. For example a natural yellow diamond of one carat is $2500, in same clarity and color a HPHT color modified diamond can come at $1000 or less.

Example 2: A natural VS1 diamond of 1 carat comes at $4000 now if the clarity is enhanced of a I1 diamond by laser drilling and fracture filling to make it VS1 then it can come in around half the price that is $1500-$2000.