A diamond is a unique gem that has unrivaled brilliance and physical properties that make it an excellent choice for an engagement ring, or any piece of jewellery that can be passed on for generations.

At Sargisons we pride ourselves on being diamond experts. On site we have three certified diamond graders and many years of experience working with diamonds.

When purchasing a diamond it is important to educate yourself with a basic knowledge of the main characteristics of a diamond. This will help you to be confident that the diamond you choose is right for your needs.

Diamonds are graded based on their physical characteristics which will dictate their resulting brilliance.

The quality of a diamond can have a large impact on the price, as well as appearance of the stone. Diamonds of the same weight (carat) but different colour and clarity can easily have a 200% difference in price. When purchasing a diamond there is always a balance to be made between price, size and quality.

Much has been written about the 4 C's of diamond grading and there are many great resources online. The Gemmological Institute of America and Auscert both have great explanations of the attributes of diamonds and are linked below:

At Sargisons we mostly stock diamonds between G and D in colour, and SI2 to VS1 in clarity. We feel that these ranges offer the best balance in terms of price and quality. We can of course source diamonds of other grades to suit your needs.

We also love coloured diamonds. We keep a range of coloured diamonds for those who are looking for something a but different.

Diamonds are commonly graded on 4 main factors, these are referred to as the 4 C's; Colour, Clarity, Cut and Carat weight.


The colour of a diamond is graded using an alphabetical scale from D (the whitest) to Z (fancy light coloured). Once they get to the higher coloured end of the scale the colours can be considered attractive and are referred to as fancy colour diamonds.

For white diamonds the less colour the better, anything G coloured or better is essentially colourless. From H down there is noticeable and increasing levels of colour.

Diamond Colour Chart



Cut in this case does not refer to the shape (round, square etc.) but to the make (the proportions of the cut stone) of the diamond. A well cut diamond will reflect more light back out of the table than a poorly cut diamond and therefore will be more brilliant. The cut of a diamond is critical and is easily overlooked.  At Sargisons we make almost everything in house and examine all stones prior to setting to ensure they are well cut.

In general a round stone will be more brilliant than a stone of another shape as the symmetry of a round stone will reflect light more efficiently.  The make of other shapes (called fancy shapes) is not as easily described and is usually not included on a diamond grading certificate.  This means that fancy shaped stones especially should be compared in person.


The most common diamond shapes are round, princess cut, emerald cut, pear cut, and cushion cut.

Diamond Shapes 



Diamonds almost all contain internal or external features that are byproducts of their formation. The size, number, nature, colour, and location of these features are graded to give an indication of the stones clarity.  Clarity is divided in to 11 clarity grades from Flawless to Included3

Clarity is graded as in the diagram below.

Diamond Clarity Scale

Anything below SI2 will have inclusions that are visible to the naked eye. Flawless stones are very rare and command a very high price. As the clarity increases the brilliance of the stone will increase as even if you cannot see the inclusions, they will intercept light as it travels through the diamond and therefore stop it coming back out.


Carat Weight

Diamonds are traded by weight. The unit of weight is the Carat which is one fifth of one gram.

A 1.00ct round brilliant cut diamond will be approximately 6.5mm in diameter.

A 0.50ct round brilliant cut diamond will be approximately 4.9-5.0mm in diameter.

Diamond Size Scale



Most of the larger diamonds that we sell are independently certified by either the Gemmological association of America (GIA) or Auscert (an Australian diamond grading laboratory). This gives you an extra piece of assurance that the diamond you are purchasing is what it is supposed to be.

It is worth noting however that not all certificates are equal. Anyone can make a certificate but for it to have any worth it must come from a reputable source. If you unknowingly buy a diamond based on an unreliable certificate you could end up paying more for a lower grade stone. This is why we always recommend seeing diamonds side by side with your own eyes, so that you can see what you are purchasing. The diamonds that we sell are accompanied by certificates from labs that we trust and we will still always verify the quality of the diamonds we sell ourselves.

Even within a single diamond grading laboratory there can still be significant variation between stones within a particular grade as demonstrated by the images below.

These are both 1.00ct G SI1 triple excellent (cut grade) diamonds with GIA certificates, and the difference is clear.

This is an example of why we believe you should always try to see diamonds in person and side by side.

At Sargisons we can have a selection of diamonds made available for you to view on an obligation free basis. We will guide you through the selection process and answer any questions that you have.



We understand that every decision we make has repercussions. The diamond industry has received criticism over the years for issues such as conflict diamonds funding armed rebel movements, or the environmental impacts of mining. These are real concerns and that is why we have chosen to take what steps we can to minimize these effects.

  • We choose to use reputable local suppliers so that we can verify that our supply chain has integrity.

This has two major benefits:

  • We have a good relationship with our local suppliers so they are happy to work flexibly with us to supply you with a broad range of carefully selected diamonds.
  • We know that our suppliers can be held accountable and will maintain the integrity of their supply chain.
  • We make things that last. The most important thing we can do for the world is consume less. We believe in making jewellery that will last a lifetime, or two,... or three. If something can be repaired we will repair it. If it can't be repaired we can usually recycle the materials and make something new.

Kimberly Process

The Kimberly process is an international protocol that has been in place since 2003 'to ensure that diamond purchases were not financing violence by rebel movements and their allies seeking to undermine legitimate governments.' (

The Kimberly process has gone a long way to prevent conflict diamonds entering the market. As of 2015 the Kimberly Process had 54 participants representing 81 countries, accounting for 99.8% of global production of rough diamonds. Our suppliers all adhere to the Kimberly process.


Difficulties with sourcing diamonds with known origin

The diamond trade is a global network with several centralized regions where certain processes take place. This has always made tracking the origin of a particular gem very difficult if not impossible. While some gems can be identified to a particular mine or region from observation of their inclusions, this is not the case with diamonds.

There are a few options if you would like to buy a diamond with a known origin. These are branded diamonds which have been traced from the mine to the market and come with a certificate of origin. There is a premium to pay for this traceability and an argument could be made that our money is just as well directed by simply buying through the Kimberly process where most of the rough is being mined in poor countries and the diamond industry is helping to support growing economies. In Botswana for example the mining companies must pay a royalty directly to the health and education system. 

We are able to source known origin diamonds and can supply both Canadian and Australian certified diamonds upon request.

Developments are being made within the industry that are making the origins of diamonds more easily traced, with new technologies making the tracking and testing of diamond rough through to finished/cut gems much more practical. At this stage however these stones still have very limited availability.

GIA for example are now offering an origin report for diamonds that have had their rough submitted for analysis prior to cutting.


Laboratory Grown

Another alternative to diamonds has come to market as technologies have improved. Gem quality laboratory grown (synthetic) diamonds are now readily available. Laboratory grown diamonds are chemically and physically identical to natural diamond. They therefor offer all the same benefits of scratch resistance, durability and of course brilliance! As natural diamonds.

We generally don't stock Laboratory grown diamonds however we are happy to supply them and can offer them for viewing on a no obligation basis just as we do with natural diamonds.

We source Laboratory grown diamonds from a local supplier and they come with a certificate from the Australian Diamond Grading Laboratory (ADGL, a reputable independent gem testing laboratory).

Laboratory grown diamonds are graded in exactly the same manner as natural diamonds with the supplied certificate clearly stating that they are of man made origin.

Laboratory grown diamonds are often marketed as an environmentally friendly alternative to natural diamonds. This is not entirely clear as the energy required to produce a diamond is huge, and they are mostly manufactured in places where coal is the main source of electrical energy. This is something that probably has no clear answer at this stage.

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