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Platinum Guide | Diamonds Guide

Dennis & Lavery Diamond Buying Guide

The most crucial process when creating any piece of fine jewellery that contains diamonds is the choice of the stones. Diamonds are selected for their CUT, COLOUR, CLARITY, AND CARAT WEIGHT (known as the 4 C's), and they must be suitable for the style, size, and function of the jewellery design.

Understanding DiamondsSenior Designer Cindy Dennis Mangan trained as a Graduate Diamond Grader at the Gemological Institute Of America (GIA) in 2006 and has a passion for selecting stones that draw gazes of admiration and amazement. Strangely this is not generally because of the size of the stones, but because they are perfectly matched to the jewellery design and to each other. Since every diamond is different it is imperative that the stones are picked and matched for the properties that are the most pertinent to the piece of jewellery being created. See below for an explanation of these properties. It must be pointed out that if Cindy was not a fine jewellery designer, she would instead be a stone picker/matcher for a living, so adamant is she about the importance of this task.

Dennis & Lavery provides an exclusive Diamond Buying & Matching Service to all bespoke jewellery clients. Please Note: We are adamant that we only source diamonds from suppliers who subscribe to the Kimberley Process which certifies the chain of custody to ensure that the rough stones are from legitimate sources. For further information about this please go to:

Properties Of Diamonds


Cut is the most obvious property of a diamond since much of it can be seen with the naked eye. The shape of the stones outline (girdle) is usually selected because of the wearers personal taste and style. For example round, square-shaped, pear-shaped, marquise-cut, baguette-cut etc. However cut is more important than just the outline shape because if a stones outline (girdle), crown height, pavilion depth, table size, and facets are cut in excellent proportion then the stone will display breathtaking levels of BRILLIANCE, FIRE, & SCINTILLATION. These terms are used to describe the way white light and flashes of colour reflect and refract and create movement within the stone and to the naked eye.

Generally the closer to ideal ratios that the proportions of cut are, the more valuable the stone, since the better the activity of light within the stone.

There are two categories of GIRDLE CUT (outline shape):

1. Round a circular girdle and therefore a round outline.

2. Fancy cut describes all girdle shapes other than round eg square, pear, oval, marquise, triangular, baguette, emerald cut etc.

There are two main categories of FACET CUT:

1. Brilliant-cut - has triangular and kite shaped facets generally radiating from the centre.

2. Step-cut - has rows of parallel facets that are step-like in appearance and are generally parallel to the girdle (outline) of the stone.

The most popular Brilliant-cut stone is the ROUND BRILLIANT.

The most popular Step-cut stone is the EMERALD CUT, rectangular with bevelled corners.


The colour of a diamond is measured on an alphabetical scale from D to Z known as the NORMAL COLOUR RANGE. At D the stone is colourless, through to Z where it is tinted light yellow or brown. Many diamonds that appear at first to be colourless often have some amount of yellow or brown tint, but are so faint that they cannot easily be detected.

Stones that display colour saturation beyond Z in yellow or brown, or in any other natural colour eg pink, blue, orange, green, are known as FANCY-COLOURED diamonds. Please note that this does not apply to colour-treated or enhanced diamonds, as only natural stones can be considered fancy-coloured. Dennis & Lavery will never use colour treated stones because there is a chance that the colour could change if it has been chemically or thermally enhanced.

Diamond colour choice is often related to the colour of the metal it will be set into, because different metals can play down or enhance colour tint in the stones.

Generally the closer to colourless the stone is, or the deeper the fancy colour, the more valuable the stone is because of its commensurate increased rarity.


Everybody has heard of the allure of the FLAWLESS diamond. This describes a stone with an absence of any distinguishing clarity characteristics either on the surface or inside the stone. However these stones are extremely rare. Most diamonds are beautiful, magnificent and completely unique, and do hold some identifying clarity characteristics.

Clarity characteristics fall into two categories:

1. Inclusions, which are internal features inside the stone itself.

2. Blemishes, which are surface irregularities.

The clarity of diamonds is measured on a scale just as colour is, however it is a descriptive, graded scale that covers the range of inclusions that might be present in or on the stone. This scale is a measure of how readily obvious the clarity characteristics are to a trained diamond grader at 10x magnification. The size, position, number, nature (type) and relief (visibility) of the clarity characteristics combine to set the grade.

GIA Clarity Scale

F Flawless: A complete absence of clarity characteristics under 10x magnification*

IF Internally Flawless: No inclusions inside, minor blemishes on the surface

VVS1 Very Very Slightly Included 1: Extremely difficult to see inclusions

VVS2 - Very Very Slightly Included 2: Very difficult to see inclusions

VS1 Very Slightly Included 1: Inclusions observed with effort

VS2 Very Slightly Included 2: Inclusions observed with effort (easier than VS1)

SI1 Slightly Included 1: Inclusions are noticeable

SI2 Slightly Included 2: Inclusions are noticeable (easier than SI1)

I1 & I2 Included 1 & 2: Inclusions are obvious and possibly the stones transparency or brilliance is affected by the size, position, and number of inclusions

I3 Included 3: Inclusions are obvious and may also affect durability

*There are three exceptions to this: a flawless diamond can have small naturals (part of the unpolished diamond skin) on the girdle that do not distort the stones intended outline shape; it can have small extra facets cut on the pavilion (base) of the stone as long as they cannot be seen from the face up position; and some internal graining is allowed as long as it does not alter the transparency nor is reflective, coloured or white.

Generally speaking the lower the number, size, position, nature, and relief of the inclusions and blemishes, the more valuable the stone.

Carat Weight

When people think of the size of a diamond, they often think in carats. However it is actually the stone weight that is measured in metric carats, not the size of the visible girdle outline. (One carat equates to one-fifth of a gram i.e. 0.200g).

Often diamonds are chosen because they weigh half a carat, a full carat, or even many carats. While diamonds are often bought in specific sizes for investment purposes, when it comes to jewellery design is it possible to create stunning pieces out of any size of stone. The most important factor when choosing the stone size is that it will complement the design and be suitable for the metal that it will be set into.

Generally speaking the higher the carat weight, the more valuable the stone, however as with the previous categories, the final value is very much affected by the other 3 Cs.

Dennis & Lavery provides more detailed advice and a Diamond Buying & Matching Service to all bespoke jewellery clients. If you would like further information or a consultation please Contact Us