Diamonds – what you need to know

A beginner’s guide to diamonds

As you probably already know, there’s more to diamonds than meets the eye. Setting out to choose one for a ring can be a daunting and stressful experience if you don’t know what you’re looking at.

To help you along your way, we’ve put together this diamond guide so you can make a more educated and stress-free decision when the time comes.

Diamond basics:
the four Cs

Diamonds are graded by their “four Cs” — Cut, Clarity, Colour and Carats (weight). Here’s a quick-fire explanation of each.

But first, an important ‘heads-up’

All four Cs are important in determining the cost of a particular diamond, and as you’ll find out, prices can vary wildly depending on how a diamond is classed within each.

That said, it’s important not to get too hung on the technicalities, especially when it comes to how a stone performs (rather than its size or weight).

Looks are pretty much everything

What really matters is how the diamond looks to you.

Sometimes stones that don’t read so well can look great ‘in the flesh’. Conversely, stones that read well just don’t live up to expectation.

Sure, get to know what you’re paying for, but let your eye be the final judge.

Just to let you know how everything went on Thursday… Ottilie said “YES”!! (but of course I knew she would). She is absolutely delighted with the ring (she literally can’t stop looking at it). It looks amazing on her finger and really suits her. The size of the ring is perfect as well, it is not difficult for her to take off, but it sits perfectly on her finger.

The diamond is truly a stunner, it looks brilliant. We couldn’t be happier!  Thanks for your assistance and guidance during the whole process. Having an Australian diamond is of special significance as well.

(You can see and read more about this ring here.)

Scott and Ottilie from Melbourne

1. Cut

Diamonds are cut with two things in mind …

  1. Keeping the most weight from the original rough stone; and
  2. Minimising the flaws and presenting the stone’s colour or “brilliance” best.

For diamonds (and gemstones too), the choice of cut is usually what will most enhance the value.

Diamonds are cut and polished to reflect light internally

The main facets of the pavilion (bottom of the diamond) are crucial to the finished look of the diamond and the angle of the cut is set by the specific gravity (density) of the stone.

Light coming in through the crown (or top) of the diamond gathers in the crown facets and bounces off the back pavilion facets and light is returned to the eye. If the facets are not aligned, there can be a loss of brilliance.

Claw settings aren’t a ‘must have’

This is why it’s okay to set diamonds in a rub-over or bezel setting. Despite common belief, you don’t need an open or claw setting to show off the brilliance of a diamond. (Some gemstones however do need light from more than one angle to best show their colour.)

Polish quality is important

The quality of the polish on facets is also important for the brightness of a diamond. Poorly polished facets will not allow enough light to go into the diamond or to reflect off facets. When polished and flat, they act like small mirrors, reflecting light back out to the eye.

Popular diamond (and gemstone) cuts

ShapeName and Description
Round (often ‘round brilliant cut’ or RBC): The most popular engagement ring diamond shape. Usually a classic ‘brilliant’ cut which features 57 or 58 facets.
Princess: Even though thought of as a ‘square’ cut, it can be (almost) perfectly symmetrical or not quite square.
Cushion: Very popular cut due to its rounded corners and general round/square hybrid-ness
Pear: An elegant choice, particularly for long fingers or those who want a unique solitaire (or multi-gem) style ring.
Oval: An uncommon choice, but an interesting one. Ovals work very well to lengthen the finger.
Radiant: Very popular cut for coloured diamonds as it can intensify the colour. Designed in 1977 as a bridge between brilliant and geometric cuts to increase the brilliance of a squarer diamond.
Heart: For the sentimental, heart rings can be adorable but the setting must be made with care.
Marquise: Quite a challenging shape but if you get it right (and buy well, because they can have bow ties (black lines through the centre)) can make very striking rings, again, be careful with the setting.
Emerald: A square version of this is known as the ‘Asscher’ cut and both are stunning in art deco-style rings.
Trilliant: Usually used as an accent stone. Often you will see a central gem (diamond or coloured stone) flanked by trilliants.

2. Clarity

Clarity refers to the visibility of flaws and impurities or inclusions (rather than their presence or absence).

Inclusions are normal in most gem materials and often aren’t visible to the naked eye.

Under high magnification many gemstones will show at least some microscopic inclusions. This can be useful to identify origin and separate naturals from synthetics.

Generally, the fewer inclusions there are, the more valuable the stone.

Along with colour, clarity is one of the major criteria used in classifying diamonds. Usually, the more ‘clear’ the diamond, the higher its value. What this means is choosing a lower grade diamond may enable you to buy a bigger stone for the same money (the exception is for high value pink, red and blue diamonds. Their rarity forgives their clarity).

Buy diamonds based on how they look, not just how they read

Depending on the location of the flaws there may be no difference in the appearance of two stones even though one has a lower clarity rating. This is why it’s important to look at the diamonds you’re buying, not just read their specifications.

Image of a ring with a diamond showing tiny bubble-like inclusions that are only visible under magnification

The tiny bubble-like inclusions in the central diamond are only visible under magnification

The best known gem grading system is from the Gemological Institute of America (GIA). Most of the diamonds we offer at EJA have GIA certification. Diamonds are graded under 10x magnification using a small magnifier called a loupe, usually table down (point facing up).

In the GIA system, there are 11 grades (from the top):

GIA clarity codes

GIA CodeDescription
FLFlawless: No loupe-visible flaws internally or externally
IFInternally Flawless: No loupe-visible flaws internally
VVS¹Very, Very Small inclusion or imperfection that is very difficult to see under a loupe
VS¹ VS²Very Small inclusion or imperfection, difficult to see under a loupe
SI¹ SI²Small Inclusion or imperfection easily seen with a loupe
I¹ I² I³Imperfect (or included): Inclusions can be see with the naked eye

Note: It’s very difficult for an untrained person to distinguish between an FL and an SI² diamond. It’s only when you get into the ‘I’ (or Piqué) grades that the imperfections start to become more visible.

The Scandinavian diamond nomenclature (Scan. D.N.) and other systems vary slightly in their classifications. The most obvious is in the I 1 to I 3 range where clarity is often referred to as P 1, P 2 and P 3 (where ‘P’ stands for Piqué — pronounced pee-kay). This is relevant for diamonds graded by HRD (Antwerp).

Position of the imperfection(s) in Piqué-grade diamonds

If your budget dictates that you must go for a lower-grade/clarity diamond, consider an ‘I’ or Piqué grade diamond with a well-placed inclusion.

If the imperfection is right on the edge of the girdle, then an inclusion could be covered by a claw or bezel when it’s set. In this case the diamond might look clear and you’ve got yourself a bargain.

Imperfections that are away from the girdle, somewhere in the middle of the stone will be visible. An unfortunately located inclusion can also block or bend light which in turn reduces the brilliance of the diamond.

3. Colour

White diamonds vary in colour from ‘colourless’ (D – J) to pale- to light-yellow (K – Z), with colourless usually being the more expensive.

A ‘lower’ colour (more yellow) diamond could cost more than an equivalent sized ‘higher’ (white) colour if the clarity and cut grading is higher.

For colourless stones, like white diamonds, less colour is better – however, depending on what you’re buying (and your partner’s taste), you’ll want either more or less.

GIA diamond colour classification

GIA Colour CodeDescription
D E FColourless
G H I JNear colourless
K L MFaint yellow
N O P Q RVery light yellow
S to ZLight yellow

Note: G to J diamonds will not actually look very ‘yellow’. To an untrained eye, it is very difficult to see ‘shades of colourless’ — and sometimes, it’s not undesirable. For example, with vintage style rings, slightly tinted diamonds (particularly in old cuts) can enhance the design.

4. Carat (weight)

Carat is the measure of weight of a diamond or gemstone. One standard metric carat is equal to 0.20 grams.

Within a type of stone, it can also serve as an indication of physical size. For example, a 1.00 carat diamond will be physically bigger than a 0.8 carat diamond of the same cut.


You’ll also often hear the term ‘point’. There are 100 ‘points’ in 1 carat. A 10 point diamond, for example, is equivalent to 0.10 carats (or one-tenth of a carat).

Many perceive the prestige attached to owning a 1.0 carat diamond ring (or bigger). But how big is a 1.0 carat diamond? The following table will give you some idea of approximate physical size relative to weight.

Round cut diamond size guide:
Diamond weightApproximate diameter (mm)
2.00ct (200 point)~8.2mm
1.50ct (150 point)~7.4mm
1.00ct (100 point)~6.5mm
0.75ct (75 point)~5.9mm
0.50ct (50 point)~5.2mm
0.25ct (25 point)~4.1mm
0.10ct (10 point)~3.0mm

Note: This rule doesn’t flow across different types of gem material. Different gemstone materials have different densities (specific gravity). Hence a 1.00-carat sapphire will be a different physical size to a 1.00-carat diamond of the same cut.

Choosing the best value combination

Colour and clarity are two major factors of the value of a diamond of any given weight, although demand is also a contributing factor – round being the most popular.

Proprietary cuts such as Hearts and Arrows™ and Lucida™ also attract a premium.

Buy the ‘best’, not necessarily the ‘biggest’

The basic rule is, “buy the best you can afford”. Weight (or size) increases cost per stone. If you can’t afford a single big diamond, consider purchasing several smaller diamonds.

Image of a trilogy style Argyle white diamond engagement ring and matching wedding ring all in recycle palladium

Trilogy style Argyle white diamond engagement ring and matching wedding ring all in recycle palladium

Size (weight) contributes to cost exponentially

Within the same clarity and colour grades, ‘small’ diamonds cost less per carat than ‘large’ ones. But popular size points like half-carat and one carat also tend to spike prices.

By buying several small stones, you can either get more carats for your money, or get the same total weight for fewer dollars.

Buying smaller diamonds also encourages creativity. Some of our loveliest designs have arisen from a need to match a budget.

Let your eye be the final judge

With all that said, sometimes diamonds surprise us.

Their grading description can ‘read’ poorly and yet blow us away by their brilliance. It’s one of those cases where the whole can be greater than the sum of its parts.

It’s because of this that it’s crucial to speak to an expert who also has your best interests at heart – not just a salesperson who needs to make target for the day.

Don’t overlook ‘alternatives’

Lab-grown diamonds are becoming an increasingly popular option over mined diamonds. You can read more about lab-grown diamonds here.

Moissanite is also a popular alternative. Whilst it does occur naturally, most commercially available moissanite is lab-grown, and is classed as a gemstone.

It’s brightness and attractive pricing make it a very viable alternative if you’re on a tight budget. Read more about moissanite here.

Want to start designing the perfect ring?

If you’d like to start designing the perfect ring for your partner (or yourself), send us a quick email (preferred) or call us on 07 3379 2596 to have friendly chat about your options.

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