What to look for when buying a Diamond: an in-depth guide

The History of diamond cutting

The four C’s for diamonds are important when buying your ring

Engagement rings have existed since the third millennium BC in almost all cultures. They were made from all types of material from gold to wire. Some were simple; others were set with jewels of all descriptions. Rings were chosen to commemorate a variety of occasions, including friendship, love, or sorrow. Rings have indeed played a significant role in relationships and are part of our social history.

Engagement rings were presented on this romantic occasion as a promise and a pledge to confirm the arrangement of the future marriage. The ring was displayed for all to see as it meant that the lady was no longer available. Chilton’s Antiques sells a wide range of antique engagement rings, many with diamonds or diamonds & other stones.

In 1477 the first engagement ring appears to have been given by Emperor Maximillian I of Austria. It was perceived in these times that the diamond would reflect the light and warn off any evil forces sent out to destroy the couple.

In Africa in the 1870’s there was a diamond rush after a young South African boy a few years earlier, had discovered a transparent rock on his father’s farm. Over the next fifteen years, South Africa yielded more diamonds than India had in over 2000 years. India prior to this discovery was the major supplier of diamonds. South Africa was a land of opportunity, Cecil John Rhodes at age 17 followed his brother to South Africa. There he became a business entrepreneur and eventually bought up many diamond claims and then finally went on to form De Beers consolidated Mines.

As we know in today’s society “diamonds are a girl’s best friend,” but what do we know about them? Since diamonds were first discovered in India 3,000 years ago, they have been put to many uses. They have been used in trade and barter, for healing properties, used for magic and adornment and even in industry. What makes a diamond so unique is not only its beauty but its properties which are unrivalled by any other natural material for its scarcity, abrasion resistance, value, resistance to chemical attack and hardness. Did you know that no other stone has been graded like diamonds? When you buy a diamond, you look for the 4C’s- CUT, COLOUR, CLARITY, and CARAT (or size).

This process was first introduced in the 1930’s as there was a surplus of diamonds and it was realised that more money could be asked for certain stones. Until this point in time, diamonds were just priced on their size.

At the same time De Beers also hired a marketing manager that came up with the marketing slogans that we still hear today such as “diamonds are forever”, “Diamonds are a girl’s best friend” or  “A month’s salary for a life time of love”.


The chemical composition of diamonds is Carbon and they have the highest thermal conductivity of any mineral. The fact that they are also very strong makes them the most sought-after mineral. There are 5 different types of diamonds and they are mined using two different methods.

Diamond crystal in rock- natural form

Alluvial- where they are dredged up from the ocean floors as in the South African coastline.

Primary- such as Kimberly Argyle mine in Western Australia.

The discovery of the African diamond deposits in 1867-1871 was the single most important event to influence the development of a grading system. With the increasing quantity of diamonds hitting world markets, their rarity and value was diminishing therefore a criteria was set up for: colour, cut & then inclusions (clarity).


Currently there are treatments that are done to diamonds to make them appear more valuable than they are. You can buy with confidence at Chilton’s Antiques as we only sell untreated diamonds. A lot of these treatments are unstable & unpredictable making them less desirable then untreated diamond.

Treating natural diamond before & after

These treatments are

  1. Clarity enhancement

* Laser Drilling 
* Fracture filling

  • Colour enhancement

* Irradiation
* Coatings
* High pressure high temperature treatments.

In the current field of new age technology much has been done to try to improve near gem quality diamonds to make them more commercially viable. This is achieved by taking a poor-quality diamond, for instance a PK clarity grading and enhancing its clarity by filling its fractures from within. The procedure entails forcing a colourless substance into the fractures to hide them. This treatment is not stable and if a diamond is subjected to heat the liquid can dry up and the stone reverts to normal with all its original faults. This includes sitting too close to a heater, washing up in hot water and even taking your rings to be cleaned or resized at a jewellers.

Most Jewellers are not gemmologists or diamond graders, so their knowledge is limited to the making, designing, and repairing of jewellery. They do not have an in depth understanding of stones and rely solely on what the wholesalers tell them, which can be a gamble.

Picture of a filled diamond as seen with purple orange flash colour

The diamond treatment process can be identified visually by turning the stone in certain angles so that light bounces off the filling and flashes of purple or orange as can be seen in the photo. This of course is not seen in untreated diamonds.

laser drilling in diamond

Another form of diamond treatment that is currently on the market is laser drilling. This is done by using a laser to drill down into a mineral inclusion and filling it up with acid that dissolves the mineral inclusion. The diamond is not affected by this, only the inclusion which is susceptible to the acid. This treatment can “improve” the diamond by ½ to full grade i.e. taking a PK stone with a visible inclusion to a grade of SI, small inclusion. Then there is a drill hole left by the laser, this can be left as an empty void or be filled up with glass. Diamonds that are treated with the glass filling have a lower melting point and cannot be exposed to heat such as any repair work that needs to be carried out, washing up in extremely hot water or even sitting too close to a heater can cause the glass filling to come out. If left unfilled by glass, dirt and dust can fill up the void making it look very dirty and impossible to clean, also leaving it susceptible to cleaving (knocking or bumping it can split in half). The drill hole can be seen under a microscope by a trained professional diamond grader as seen in the photo above.

inclusions seen in diamonds

At Chilton’s we check for any treatments by having our diamond graders check all stones, regardless of what is stated on accompanying certificates. We also make sure certificate matches the stone & we can also verify it is not a forgery.


Perfect proportions with diamond cutting

Too shallow: Light is lost out the bottom causing the diamond to lose its brilliance.

Too Deep: Light escapes out the sides causing the diamond to become very dark and dull in appearance.

Given the example of two stones both of the same colour, clarity & size, one of which has a lot of sparkle and is better able to handle light, the other being badly cut with all the wrong proportions, which diamond would you want? Badly cut stones may be disguised by numbers and percentages in Valuation Certificates. The ideal percentages are all different they depend on the stone’s shape which will determine its fire and its brilliance. The best way to work out whether a diamond is well cut is to be able to hold it near light and make sure it look bright or to seek advice from professional diamond dealers such as Chilton’s, where we take all the worry and stress out of buying a diamond.

modern diamond cutting

Development through the ages of the diamond cutting technology

The evaluation of diamond cutting

Rose cut

Rose cuts were invented in the mid-16th century, it was also known as the Antwerp rose, Crowned Rose Cut, Dutch Cut, and the Full Holland Cut. The Rose cut forms a single hemisphere for a total of 24 facets or it can be two back-to-back hemispheres (Double Dutch Rose) forming a total of 48 facets. This cut was also often foiled from behind to create more dispersion.

cutting of a rose cut

Old Mine Cut – 1700s

The “old mine” cut is the earliest form of the “brilliant cut” diamond.

This Old Mine cut is basically square with gently rounded corners and “brilliant” style facets. The crown is typically tall, resulting in a smaller table. The culet cut off leaving an eye effect (hole in the middle) that is visible when looking down into the stone from the table.

Old cut diamond cut

Old European Cut – 1800s

Table of diamond cuts

The “Old European” cut was the prototype of the modern Brilliant Cut. The Old European diamond cut has a very small table, a heavy crown, and very tall overall depth. Like the modern round brilliant, the old European diamond has a circular girdle.

The Modern Round Brilliant Cut

The evaluation of diamond cutting

The modern round brilliant cut diamond was developed by Belgian diamond-cutter Marcel Tolkowsky in 1919. This cut is also known as the “Tolkowsky Cut” and “Tolkowsky Brilliant.” Even with modern techniques, the cutting and polishing of a diamond resulted in a loss of as much as 50% of the stone’s total weight. The round brilliant cut was a partial solution to this problem. This Modern Round Brilliant Cut Diamond came into prevalence between the 1950’s- 1960’s when technology advancements had improved.


colour grading chart

Diamonds come in a wide range of colours. The main scale is the colourless scale D-Z. Diamonds are graded on this scale from colourless to yellow with a letter from the alphabet allotted to each colour grade. The colour scale starts at D and descends to Z. Lower than Z in colour is termed fancy diamond & the price begins to soar again due to their rarity. The most expensive diamonds in this series are colourless stones. The less colour in a diamond, the whiter light can pass effortlessly through and be dispersed as rainbows of colour on top.

What causes the yellow colour in diamonds? Nitrogen in the earth causes that yellowness in the stones. Obviously, there are many yellow stones on the market, and this makes the white stones highly sought after and maintains their price-because they are rarer. Australia produces 40 million carats per year: 52% for industrial use (saw blade tips, cutting devices etc) and 40% is near gem quality, with only 5% actual gem quality. In the current market today unfortunately most of the so called “bargain” diamonds found on the internet and in the chain “low cost stores” are of industrial quality.

When choosing a diamond Chilton’s recommends you look no lower than H-I grading. Also remember that not all diamonds are correctly graded! Many certificates display incorrect grading from careless or non-qualified retailers.


The observation of internal features and faults in diamonds for commercial purposes began at the beginning of the 20th century in Paris. Paris at the time was the centre for the trade in diamonds. In the 1930’s the GIA bought in the first quality grading system. A perfectly clear diamond which is free from inclusions is a very rare find. Most diamonds contain very tiny inclusions that like fingerprints make each diamond unique and identifiable. Diamonds can really have their own ‘DNA’ (characteristic set of markings), Mother Nature’s fingerprint. The fewer the inclusions, the more the diamond will sparkle. A diamond’s clarity can only be determined by using an x10 magnification and a trained eye. Letters are used to denote clarity grades: FL, IF indicate a flawless or internally flawless diamond or LC (loop clean); VVS means very, very small inclusions that are not visible to the naked eye these can be 1 or 2 type inclusions; VS simply means very small inclusions, again not visible to the naked eye; SI means small inclusions and I or PK means that inclusions can be detected by the naked eye and indicate a poorer quality diamond. Diamonds are only put into these sub grades of 1 & 2 over the size of 0.40cts.

Diamond grading chart

Chilton’s recommends the grading from VS to SI Clarity.


Carat refers to the weight of the diamond. One carat is divided into 100 points and generally if a client wants a larger size diamond, they sacrifice some clarity and colour to achieve size. If you want the best of the 4 C’s be prepared to pay a premium for this. There is no substitute for quality.

There is plenty to think about before buying a diamond ring and the best advice that can be given to anyone buying a diamond is to do just that- get the best advice. Go to someone who is knowledgeable, trained and reputable and who is prepared to take the time to explain the diamond you are buying. Unlike many other large purchases like cars or even houses diamonds are usually kept for the lifetime of the wearer because of their sentimental value and are looked at every day by the wearer, so getting it right is important. Chilton’s is well known for its range, ability to source stones, variety of styles and quality of service to customers and has registered Valuers and Diamond Graders in the store at all times to advise you on your diamond selection.

Diamond grading chart


Wide range of diamond shapes

Diamonds now come in a wide variety of shapes for you to choose from:

Diamond imitations: Synthetic diamonds, cubic zirconia & moissanite

Synthetic VS Natural diamond

Man-made diamonds, also known as synthetic diamonds, have been around since 1950’s but have only recently being offered for sale in commercial retail store. Synthetic diamonds are stones that are grown in highly controlled laboratory environments using advanced technological processes that duplicate the conditions under which diamonds naturally develop when they form in the mantle, around 85 miles beneath the Earth’s crust over a period of billions of years. Once the diamond has been naturally created through extreme heat & pressure by the earth, it travels via molten rock to the earth’s surface where it stays dormant until it is mined.

Synthetic or man-made diamonds consist of actual carbon atoms arranged in the characteristic diamond crystal structure, so they have the same molecular structure as their natural counterparts. Since they are made of the same material as natural diamonds, they exhibit the same optical and chemical properties. These stones will look identical to a natural diamond, the only difference being one is made artificially, and one is made in the earth naturally. One of the major differences is they are not as hard as a natural diamond registering slightly less than a diamond on the Moh’s hardness scale (see table below).

It is important to note the major differences between laboratory grown diamonds and diamond simulants. Diamond simulants, such as cubic zirconia and moissanite can look similar to diamonds but are not true copies. Simulants do not have the same chemical and physical properties as natural diamonds and therefore sell at much lower prices than man made diamonds. Simulants can be distinguished from natural or laboratory grown diamonds using only the naked eye.

Natural and laboratory grown diamonds have thermal conductivity properties that differentiate them from cubic zirconia with a handheld diamond tester. Some laboratory diamonds, along with some natural coloured diamonds, may be mistakenly identified as moissanites when using certain diamond testers due to similarity in their electrical conductivity. However, gemmologists can typically distinguish between diamond and moissanite due to their differing refractive properties, with moissanites being double refractive and diamonds being single refractive. Despite synthetic diamond companies & some retailser saying gemmologists cant tell the difference between natural & synthetic diamonds, which is totally false a gemmologist can tell the difference between HPHT & CVD diamond & a natural stone. Gemmologist use a variety tools spectroscope, UV & even a magnet to tell difference. Synthetic stones will only get cheaper while natural stone will hold its value.

Synthetic diamonds are around a half of the price of a natural diamond.


The mineral moissanite was first discovered by a scientist Henri Moissan while examining rock samples in a meteor in 1893 in Arizona. At the time he thought they were diamonds but later he re identified them as silicon carbide.

cubic zirconia vs natural diamond vs moissanite

Moissanite was introduced into jewellery market in 1998 after C3 INC, Charles & Colvard were granted a patent to re-create & market laboratory grown silicon carbide crystals. Charles & Colvard marketed moissanite as a lower price alternative to diamond. These stones are better quality than cubic zirconia as they wear better. The only difference between moissanite & CZ is that moissanite have a stronger colour dispersion, you can see more of a rainbow colour through the stones; they are unnaturally bright so they can look somewhat slightly fake & they are double refractive with a mirror effect inside the stone.

Many clients have used them as a temporary stone, which they can afford now but will replace at a later time. They last longer and look better than a CZ with wear & tear.

Depending on the age of the moissanite and which generation stage it is from, as with time the company has developed better technology and is now able to create whiter looking stones. When moissanite first came out on the market the colours range was I-K with a definite yellow tint- the new generation of moissanites are much whiter E-F -G colour ranges.

Cubic zirconia

Cubic zirconia (also known as CZ) is similar looking to a diamond with its brilliance and crystal clarity, but it is a synthesized (man-made) crystalline material that is colourless, hard, and flawless. It looks very much like a diamond; it is an affordable alternative to a diamond. It can made in different colours to simulate the different colours of a diamond.

Cubic zirconia started being produced in the 1970’s because of its diamond-like qualities, it’s very low cost, and overall durability.

Cubic zirconia crystals are made by melting powdered zirconium and zirconium dioxide together in a laboratory and heating them up to 4,982ºF. A cubic zirconia is a perfectly man-made, flawless looking stone.

There are some ways to distinguish cubic zirconia from a diamond as follows:

  • Thermal conductivity: Diamonds are thermal conductors while cubic zirconia is a thermal insulator. This is what makes the diamond stand out next to the cubic zirconia with special diamond testing machines.
  • Hardness: Diamond has a rating of 10 and Cubic zirconia has an 8 on the Mohs hardness scale. See table below. With time CZ do scratch & have parcel wear over top of the stone.
  • Density: Cubic zirconia is 1.7 times denser than a diamond. Often powder remanence is often seen a small cloud particle in some stones. Other batches are better well-formed and flaw less.
  • Refractive index: Diamond has a refractive index of 2.42 vs. Cubic Zirconia has an index of 2.15-2.18
  • Cut: Diamonds are typically cut differently than cubic zirconia gemstones. This is due to cost factor; a lot of time is spent on cutting a CZ as its not cost effective whereas cutting on a diamond is generally a lot better as more time goes into the process. The old saying you get what you pay for applies here.
  • Dispersion: Diamond 0.044 vs. cubic zirconia 0.058-0.066
  • Colour: Cubic zirconia is equivalent to the perfect “D” on a diamond’s grading scale, but it also comes in other colours as well.

My final thoughts as a Diamond Grader, Registered Valuer & a woman for the many jewellery lovers is that there simply is no substitute for a natural diamond. You will always know yourself it is fake; it is like owning a fake designer handbag. A woman deep down knows the difference. I feel that there is a marketplace for moissanite & cubic zirconia as they are priced accordingly & are usually worn as fun dress jewellery, but I feel the price difference for synthetic stones is too high they are not value for money. That is why at Chilton’s we do not sell synthetic diamonds & never will. Synthetic diamonds will never keep their value when comparing them to natural diamonds.

Chiltons expertise & affiliations:

At Chilton’s Antiques at Miranda we make it our business to know about diamonds and to make sure our customers are well informed about their diamond purchase. We have a Registered NCJV Valuer in the store- Liz Stevens, who is a skilled Diamond Technician and Diamond Grader & is happy to share her skills and knowledge with all customers, when they are making such an important purchase as a diamond engagement ring or dress ring. Examinations and grading of the diamonds is done in our store and all diamonds purchased come with a qualified valuer’s certificate. With Chilton’s you know that the diamond you buy is exactly what you are paying for. If you have any further questions about diamonds, visit us instore or give us a call on (02) 9254 0630

GAA Member

We also personally guarantee that we buy “Non conflict Diamonds”.

We also offer sustainable stones, recycled antique & vintage stones.

Liz Stevens

Fellow of the Gemmological Association of Australia (FGAA) Gemmologist, member of the  National Council Jewellery Valuers (NCJV), accredited member of the CINOA Federation (Confédération Internationale des Négociants en Oeuveres d’Art), member of the AAADA Antique & Art Dealers Association of Australia, Diamond Grader & a Diploma of Diamond Technology from Gemmology House, Sydney.

NCJV Member 543


About Elizabeth Stevens

As the Principal of Chilton's Antiques and with close to 30-years experience in the industry, CINOA, AAADA and NCJV noted expert, Liz Stevens is a consummate professional. Lecturing and writing papers on Gemology and Antique pieces internationally, as well as hosting a 7-year running Antiques Radio Show on 2UE.