Humberstones Jewellers is a second generation jewellers that specialises in fine diamonds and diamond jewellery. Buying a diamond can be a daunting task, and we at Humberstones want to take away any of the stress we can for you, to ensure a smooth transaction in which you feel confident, and comfortable, you are making the right decision.

We have created this short guide, to give you an insight into the considerations to make when choosing your diamond. Our staff will ensure this is an exciting and memorable time for you. Read below to learn all about the ‘4 C’s’; Cut, Colour, Clarity and Carat.


A diamond cut is a style or design guide used when shaping a diamond for polishing. Of the 4 C’s, cut is often considered the most important characteristic, as it has the greatest influence on the diamonds sparkle. 

A number of different cuts have been developed that will best show a diamonds material properties. 

Please click on the links below to learn more about the different cuts: 

Brilliant Cut Diamonds 

Pear Cut Diamonds 

Marquise Cut Diamonds 

Princess Cut Diamonds 

Emerald Cut Diamonds 

Radiant Cut Diamonds 

Trilliant Cut Diamonds  



The carat weight of a diamond refers to the actual weight of a diamond. One carat is defined as one fifth of a gram or 200 milligrams. A carat can further be divided into 'Points'. One Point of a carat is equal as 0.01ct so in one carat there are 100 points. The size of a polished diamond is related to its carat weight. It is important not to confuse Carat weight with size. There are other aspects of a diamond that can affect how large an individual stone actually appears, most importantly the cut and shape of a diamond. 






Colour refers to the colourlessness or the lack of colour in a diamond. Although many diamonds appear to be colourless, most of them would exhibit at least hints of yellow or brown. The yellower the stone, the lesser its value.

The Colour of a diamond has a huge impact on its value. The most treasured diamond colour is actually the "colourless" grade one without any colour at all.

The diamond colour scale was devised by the Gemological Institute of America (GIA) in the mid 1950's to regulate and define the colour spectrum of diamonds. The GIA proposed starting at D as the best and most colourless diamond available [Why D and not A? well just in case anything better is ever found]. The colour scale progresses through the alphabet from D until Z which is the most colourful diamond. The graphic below illustrates the GIA colour scale.

At Humberstone Jewellers we find only the finest diamonds with colour graded D-I. Diamonds graded better than J are colourless or near-colourless — their colour is typically undetectable to the unaided eye.





Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects called blemishes. Inclusions may be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. A clarity grade is assigned based on the overall appearance of the stone under ten times magnification.

Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. However, large clouds can affect a diamond's ability to transmit and scatter light. Large cracks close to or breaking the surface may reduce a diamond's resistance to fracture.

Diamonds with higher clarity grades are more valued, with the exceedingly rare Flawless graded diamond fetching the highest price. Minor inclusions or blemishes are useful, as they can be used as unique identifying marks analogous to fingerprints. In addition, as synthetic diamonds technology improves and distinguishing between natural and synthetic diamonds becomes more difficult, inclusions or blemishes can be used as proof of natural origin.



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


  • Flawless category (FL) diamonds have no inclusions or blemishes visible under 10x magnification.
  • Internally Flawless category (IF) diamonds have no inclusions visible under 10x magnification, only small blemishes on the diamond surface.
  • Very, Very Slightly Included category (VVS) diamonds have minute inclusions that are difficult for a skilled grader to see under 10x magnification. The VVS category is divided into two grades; VVS1 denotes a higher clarity grade than VVS2. Pinpoints and needles set the grade at VVS.
  • Very Slightly Included category (VS) diamonds have minor inclusions that are difficult to somewhat easy for a trained grader to see when viewed under 10x magnification. The VS category is divided into two grades; VS1 denotes a higher clarity grade than VS2. Typically the inclusions in VS diamonds are invisible without magnification, however infrequently some VS2 inclusions may still be visible. An example would be on a large emerald cut diamond which has a small inclusion under the corner of the table.
  • Slightly Included category (SI) diamonds have noticeable inclusions that are easy to very easy for a trained grader to see when viewed under 10x magnification. The SI category is divided into two grades; SI1 denotes a higher clarity grade than SI2. These may or may not be noticeable to the naked eye.
  • Included category (I) diamonds have obvious inclusions that are clearly visible to a trained grader under 10x magnification. Included diamonds have inclusions that are usually visible without magnification or have inclusions that threaten the durability of the stone. The I category is divided into three grades; I1 denotes a higher clarity grade than I2, which in turn is higher than I3. Inclusions in I1 diamonds often are seen to the unaided eye. I2 inclusions are easily seen, while I3 diamonds have large and extremely easy to see inclusions that typically impact the brilliance of the diamond, as well as having inclusions that are often likely to threaten the structure of the diamond.