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Diamond Guide

All of our diamonds are set using the latest technology to ensure that the diamonds not only look at their best, but are also secure long term. Our diamond setters use high power microscopes and pneumatic engraving tools for precise high quality work.

The 4 C's

In order to work out a diamonds value and quality there is a standard way of appraising it, by using criteria called the 4 C's. The 4 C's are the Clarity, Carat, Cut and Colour of a diamond. Diamond appraising is a complex task with only very minor differences between grades which can only be determined using the relevant tools and under strict lighting conditions.

To try and simplify diamond appraising the 4 C's are explained below in greater detail.

Diamond Clarity

Diamond Clarity relates to the number of imperfections a diamond has. These imperfections are called inclusions, which are technically anything from minute cracks to small traces of non crystallised carbon. Diamonds are natural products and invariably will have inclusions to some degree, however the fewer the inclusions the better.

Diamond clarities such as SI 1/2 provide a diamond that technically has inclusions but do not show to the human eye, and are only apparent upon magnifying the diamond. These clarities offer a good balance of appearance and value for money.

To grade a diamond's clarity a gemmologist will use a 10x magnification glass also known as a jeweller's loupe to zoom in on the diamond and analyse the clarity.

Diamond Guide

Below are the standardised levels used for expressing a diamond's clarity:

  • IF - absolutely free from inclusions, no imperfections visible through a 10x loupe.
  • VVS 1/2 - very very small inclusions, nearly invisible through a 10x loupe.
  • VS 1/2 - very small inclusions, barely visible through a 10x loupe.
  • SI 1/2 - small inclusions visible through a 10x loupe but invisible to the naked eye.
  • P1 - inclusions immediately evident with a 10x loupe though hard to see with the naked eye.
  • P2 - large/numerous inclusions visible to the naked eye and affecting brilliance.
  • P3 - large/numerous inclusions very visible to the naked eye and affecting brilliance.

Diamond Carat

Diamond carat relates to the weight of a diamond. Diamond carat does not relate to the size of a diamond.

One carat weighs precisely 200mg or milligrams.

Jewellery that comprises more than one diamond will have a total diamond weight. Total diamond weights are not as valuable as the equivalent individual diamond weight, i.e. a ring with five diamonds with a total weight of 1 carat is not as valuable as a ring with one diamond weighing 1 carat.

Big diamonds have bigger prices, as the size of a diamond increases so does the rarity and value. For example a 2 carat diamond is around four times as valuable as a 1 carat diamond of equal quality.

The chart below will help you understand the approximate size of a diamond for its stated weight.

Brilliant Cut Diamonds
Carat Size (mm)
0.10 3.00
0.15 3.40
0.20 3.80
0.25 4.10
0.30 4.40
0.40 4.70
0.50 5.00
0.75 5.80
1.00 6.50
2.00 8.20
Princess Cut Diamonds
Carat Size (mm)
0.10 2.70
0.15 2.90
0.20 3.20
0.25 3.50
0.30 3.80
0.40 4.00
0.50 4.40
0.75 4.90
1.00 5.50
2.00 7.00

Diamond Cut

Diamond cut determines two things about diamonds.

Firstly it refers to the actual shape of a diamond (e.g. round, square, oval etc). Round shaped diamonds are actually called brilliant cut diamonds and square shaped diamonds are called princess cut diamonds. The chosen shape of a diamond will determine the pattern used and how the diamond is actually cut and formed by a diamond cutter.

Once a diamond has been shaped the diamond cut usually then refers to the proportions, symmetry and polish of a diamond. These are some of the most important factors for a diamonds overall finish, and will determine how well a diamond will sparkle.

The proportions of a diamond are very important as there is an ideal ratio of width by depth for every weight. For example a 1 carat brilliant cut diamond could actually have a width of less than 6mm rather than the ideal 6.5mm and be a deeper stone, which would obviously offer less appearance once set in a ring and actually look like a smaller 0.75 carat diamond, but cost a lot more. An ideally proportioned diamond is usually achieved at the expense of losing some of the diamonds weight, which is why bigger isn't always best.

A diamonds symmetry relates to how well aligned the facets of the diamond are. Alignment is one of the main contributing factors in how much a diamond sparkles, as this determines how the light travels through the diamond. Ideally when light enters a diamond it should be reflected out at the top towards the person looking at it, not out of the side or downwards as a poorly cut diamond would.

The polish of a diamond is how smooth or rough the facets are, and the smoother the facets the better. A diamond with excellent polish can be likened to a well polished car, offering amazing depth and shine.

Diamond Colour

The colour of a diamond is based upon a standardised scale which is set by The Gemological Institute of America. In order to determine a diamonds colour a set of master stones are used to compare diamonds side by side with the masters. A gemmologist will perform this comparison under strict lighting conditions.

GIA’s diamond colour grading scale:

  • Colourless - D, E, F
  • Near Colourless - G, H, I, J
  • Faint - K, L, M
  • Very Light - N, O, P, Q, R
  • Light - S, T, U, V, W, X, Y, Z

There are only very few diamonds in the world that are truly colourless, and these are the most expensive of diamonds assuming they are of excellent clarity, cut and carat. Generally speaking the more colour a diamond has the less valuable it becomes, although there are exceptions for very rare fancy colours.

It is also worth noting that the surrounding environment can affect a diamonds colour, this is why it's best to let an expert gemmologist asses a diamond's colour under strict lighting conditions.

Conflict Diamonds

We only select diamonds that are ethically sourced and free from worldwide conflict.

Jewellery Assessment Report

SafeGuard Jewellery Assessment

For additional peace of mind when purchasing stone set rings from us, we can also offer a SafeGuard Jewellery Assessment Report. The report is an independent expert assessment carried out by SafeGuard, who are part of the Birmingham Assay Office.

The report is an overall description of the ring, but also includes:

  • Diamond Quality
  • Diamond Sizes and Gross Weights
  • Precious Metal Type
  • Digital Photograph of Ring
  • Individually Hologrammed Booklet

The standard timescale for a Jewellery Assessment is approximately 1 week, although an express service is also available.

We cannot offer a refund on Jewellery Assessments, however we are happy to send your jewellery for appraisal after you have tried it first.

Please note: The SafeGuard Jewellery Assessment is not a valuation service, for Independent Valuations we use SafeGuard Valuations.