The Ultimate Guide to Buying Diamonds

The Ultimate Guide to Buying Diamonds

Each Diamond, like a human finger print, is unique. Formed in the earth billions of years ago, there are no two Diamonds the exact same. However, Diamonds can significantly vary in both appearance and cost depending on a number of factors.

The Cut, Colour, Clarity and Carat weight of a Diamond, known as the 4 C’s, are the most important factors to consider when making a Diamond purchase.

Focus on the factors which are most important to you, and choose a Diamond which suits your budget and your standard of beauty. Some clients opt for finger coverage over clarity and colour, while others prioritise the cut over the carat weight. At Lancastrian Jewellers, we want to help find you the best Diamonds and jewellery for you.


The Diamond cut is an important element to consider when buying a Diamond. The cut determines the sparkle and fire of the stone, and even a very high quality Diamond can appear dull and lifeless if the cut is poor.

Each Diamond is cut with artistry and mathematical precision, to ensure the proportions are correct to create a stone which truly sparkles and disperses light.

An excellent Diamond cut will ensure light going into the stone is returned out of the top of the stone (creating sparkle). If a cut is too shallow or deep, the light will not correctly disperse from the stone, and therefore the brilliance of the sparkle is lost.


GIA Anatomy of a Diamond.

Source - GIA.


The colour grading of Diamonds actually refers to the lack of colour in the stone. The highest quality Diamonds are colourless, while those of lower quality will have noticeable colour, which manifests as a pale yellow in Diamonds.

The Gemmological Institute of America’s (GIA) grades Diamond colour from D (colourless) to Z (light yellow or brown). D-Z diamonds are all known as white diamonds, even though most diamonds from I/J onwards have a faint yellow tone.

Diamond Ring

The scale:

D colour is the highest grade and is extremely rare.

Like D colour diamonds, E and F colour diamonds are rare but have minute traces of colour – unnoticeable to the naked eye.

In G colour diamonds, the very slight warm tone is difficult to detect unless compared side-by-side with diamonds of better grades.

The faint yellow hue is also difficult to detect in H colour diamonds, both G and H colour Diamonds provide excellent value.

Still at great value, the slight yellow tint of I and J colour diamonds are only detected when compared side-by-side with diamonds of H grades or higher.

From K colour diamonds on, colour is visible to the naked eye. Most feel these diamonds have too much of a warm colour. K colour diamonds are usually half the price of G colour diamonds.

For the best value, choose G-J diamond colour grades as with these diamonds, the naked eye can’t discern any colour, but the cost savings are significant when compared to those with higher grades.


Source - GIA.


Diamond clarity is the assessment of small imperfections on the surface and internally. The surface flaws are called blemishes, and internal defects are known as inclusions. These tiny, natural blemishes and inclusions are microscopic and do not affect a diamond’s beauty in any way. However, Diamonds with the least and smallest inclusions receive the highest clarity grades.

Inclusions are known as – clouds, feathers, crystals, knots, cavities and graining.

Blemishes include – polish lines, scratches, nicks, pits, chips, breaks and dark spots.

The GIA diamond grading scale is divided into six categories and eleven diamond clarity grades:

Flawless (FL) Diamonds – Inclusions and blemishes aren’t visible on flawless diamonds, even under 10x magnification. A flawless diamond is incredibly rare with less than 1% of Diamonds in the world being classed as flawless!

Internally Flawless (IF) Diamonds Inclusions aren’t visible in internally flawless diamonds under 10x magnification, however some small surface blemishes may be present.

VVS1, VVS2 Very Very Slightly Included (VVS) Diamonds VVS diamonds have miniscule inclusions that are difficult even for trained eyes to see under 10x magnification. VVS2 clarity diamonds have slightly more inclusions than the VVS1 grade.

VS1, VS2 Very Slightly Included (VS) Diamonds – VS diamonds have minor inclusions that cannot be seen without 10x magnification. VS1 is a higher clarity grade than VS2, which may have further inclusions.

SI2, SI1 Slightly Included (SI) Diamonds – Inclusions are noticeable at 10x magnification with SI diamonds. With SI1 and SI2 diamonds, inclusions are sometimes visible to the eye without magnification.

I1, I2 and I3 Included Diamonds – I1 diamonds have minor inclusions that may be visible to the naked eye. I2, I3 are heavily Included Diamonds which are visible to the naked eye.

For the best value, select a diamond with inclusions that can’t be seen without magnification (also known as eye-clean diamonds), such as an SI or VS clarity grade. These diamonds are much less expensive than the extremely rare Flawless (FL) or Internally Flawless (IF) diamonds.

Diamond Ring



Diamond carat is often misunderstood and refers to a diamond’s weight, not necessarily its size. When comparing diamond carat sizes, take a diamond’s cut into consideration as well: a high-carat diamond with a poor cut grade may look smaller, often cut deeper, than a diamond with smaller carat weight and a better cut.

Carat weights are often written like this – 0.25ct, 0.50ct, 1.0ct, 1.5ct.

The higher the number the larger / heavier the stone. Each carat can be subdivided into 100 ‘points’, allowing very precise measurement. The more a diamond weighs the more valuable it becomes, as larger diamonds are very rare.

When buying a Diamond, keep in mind that the smaller the finger, the larger the diamond will appear. For example, A 1.5-carat diamond solitaire looks much larger on a size 4 finger than a size 8.

Also keep in mind that a 1.5ct VVS1 F colour Diamond is going be more expensive than a 2.0ct SI H colour Diamond – sometimes if you want a good size stone for a smaller budget you can compromise on the clarity and colour.

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I hope this guide has helped you in your Diamond shopping! For further help or assistance when buying a Diamond please don’t hesitate to contact me.

Here at Lancastrian Jewellers, we stock a great range of jewellery from antique pieces to modern classics, we have something for everyone.
You can browse more of our Diamond Jewellery here.
Please get in touch if you need any further help finding the perfect piece of jewellery.

Further Reading:

If you'd like to expand your knowledge on Diamond jewellery even further, we recommend taking look at the links below. 
1. Before Buying a Diamond: 9 Tips You Should Know - IGS.
3. Diamond Buying Guide - Fraser Hart.


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