Diamonds - Information and Diamond Jewellery Buyers Guide




Natural diamonds have captivated humanity for centuries with their exquisite beauty and enduring value. These precious gemstones, formed deep within the Earth over millions of years, hold a special place in peoples hearts and have come to symbolise love, commitment, and luxury.

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The Formation of Natural Diamonds:

Natural diamonds are created under intense heat and pressure deep within the Earth's mantle by carbon atoms being formed into a crystal lattice. A diamond may take millions of years to make it's way up through the Earth's crust to a point where we are able to mine it.  Owning a diamond is owning a piece of ancient history created long before mankind walked the Earth.


Diamonds in Jewellery

Diamonds are ideal for jewellery, they are hard and tough and with basic care will easily last several generations allowing you to pass them down as heirloom jewellery.  When expertly cut they have a brilliant sparkle and fire which captivates and lasts.  Their hardness makes them ideal for jewellery worn everyday such as rings or pendants.  They will not discolour or change over time and are easily cleaned and will not be harmed by everyday chemicals, chlorine in swimming pools etc.  Although very tough they can be chipped, so it is best to remove diamond jewellery if you are undertaking rough manual work.


Diamond Value

The value of a facet cut diamond is based on the Four C's (see below).  In general the two factors which carry the most weight are the Clarity and Weight (carat) with the colour and cut having a lesser effect (although there are exceptions for poor colour or cutting).

Prices vary over time and depend on market conditions, when purchasing.  Diamonds which have high scores on all 4 of the metrics they will retain their value (and often increase in value) over time and are the best for long term investment.  For day to day jewellery a diamond nearer the middle of the range will be much more affordable and be practically indistinguishable from a higher grade when mounted.


Diamond Quality - The Four C's

Diamond quality is assessed by the four C's - Clarity, Colour, Cut and Carat


Natural diamonds normally have small imperfections such as carbon and other minerals trapped inside, tiny fractures and fault lines or blemishes.  The most commonly used standard to define clarity is that of the GIA which defines clarity as:

  • Flawless (FL) No inclusions and no blemishes visible under 10x magnification
  • Internally Flawless (IF) No inclusions visible under 10x magnification
  • Very, Very Slightly Included (VVS1 and VVS2) Inclusions so slight they are difficult for a skilled grader to see under 10x magnification
  • Very Slightly Included (VS1 and VS2) Inclusions are observed with effort under 10x magnification, but can be characterized as minor
  • Slightly Included (SI1 and SI2) Inclusions are noticeable under 10x magnification
  • Included (I1, I2, and I3) Inclusions are obvious under 10x magnification which may affect transparency and brilliance

At Blue Cherry Antiques we grade diamonds (where possible) on the conservative side of the scale.  As diamonds are already set in jewellery grading is done to the best ability within the limitations of visibility.  We use a 10x magnification Nikon binocular microscope for checking gems, this is much more exacting than a 10x hand held loupe which is the most common tool used.


It is the lack of colour that determines another factor of diamond quality.  The scale for colour is D to Z with D being colourless and becoming increasingly yellow along the scale.

  • D-E-F are considered colourless
  • G-H-I-J are considered near colourless
  • K-L-M are considered faint yellow
  • N-O-P-Q-R are considered very light yellow
  • S-T-U-V-W-X-Y-Z are considered light yellow

Diamonds are colour graded under controlled light and background against a reference set of stones.  Stones mounted in jewellery are difficult to grade accurately and may pick up colour from the metal setting so best estimates are used.  Stones below 1/4 carat can be near impossible to accurately grade when mounted and the colour is estimated.

For general jewellery use a diamond from D to J below 1 carat size will not exhibit any noticeable colour for the wearer.


The 'cut' of a diamond in relation to quality depends on a number of factors (not the shape or style of the cut), these are:

Proportion: The proportions of a diamond's cut play a pivotal role in how light interacts with the stone. Well-proportioned diamonds are designed to maximize the reflection and refraction of light, resulting in a dazzling display of brilliance and fire. On the other hand, poorly proportioned diamonds may appear dull and lifeless. When assessing diamond cut quality, gemmologists consider the proportions of the stone, including the table size, crown height, pavilion depth, and girdle thickness.

Symmetry: Symmetry refers to the precise alignment and balance of the diamond's facets. A diamond with excellent symmetry will exhibit a harmonious display of light performance. Conversely, diamonds with symmetry issues may display distorted patterns of light and shadow, detracting from their overall beauty. When examining diamond cut quality, paying attention to the symmetry of the stone is paramount in determining its visual appeal.

Polish: The polish of a diamond refers to the smoothness and overall condition of its surface. A well-polished diamond will showcase flawless surfaces and crisp facet edges, allowing light to travel unimpeded through the stone. Conversely, diamonds with poor polish may have surface imperfections that hinder the passage of light, diminishing their brilliance. Evaluating the polish of a diamond is a crucial aspect of assessing its cut quality, as it directly impacts the stone's visual clarity and sparkle.

Important points of assessing cut are:

  • Brightness: Internal and external white light reflected from a diamond
  • Fire: The scattering of white light into all the colours of the rainbow
  • Scintillation: The amount of sparkle a diamond produces, and the pattern of light and dark areas caused by reflections within the diamond

For diamonds set in vintage jewellery it is generally very difficult to accurately assess the cut quality especially for diamonds below 1/2 carat in size.


The carat of a diamond is simply it's weight with the unit being a 'carat'.  One carat is 200 milligrams metric weight and for gemmology and jewellery purposes a carat is also divided into 'points'.  One carat = 100 points, so a 20 point diamond is 1/5 carat for example.

If you can measure the diamond then you can use a mathematical formula to estimate its weight, although this is never quite perfect as slight differences in the facets and cut will skew the result.  If the diamond is not mounted in jewellery it can be weighed on specialist scales for a near perfect result.  When set in jewellery carat weights are estimated within the limits of accurate measurement.

Diamond Certification

Diamonds can be tested and certified by specialist laboratories, perhaps the best well known being the GIA.  Gems are tested by specialists using advanced tools to certify their quality (the four c's), their origin (natural or synthetic), and any treatments or enhancements they have received.

These tests are best done on unmounted stones before they are set into jewellery, and a certificate from a respected laboratory will increase the value of the gem.  However such testing is not cheap with prices currently around £120-250 ($150-300) for a comprehensive certification.  While worthwhile for higher value pieces for everyday jewellery it is generally not done as it significantly increases the cost for little benefit to the consumer.

It is important to note that mounted diamonds cannot be tested to the same standard and only certain criteria can be checked, results will also be less accurate.  Also note that there are many labs (especially labs in India and China) which provide credit card type certificates with stones.  The value of these certificates is limited and cannot be relied upon for accuracy or honesty and they are often more of a marketing exercise than an impartial test.


Diamond Enhancements

Natural diamonds are sometimes subjected to 'enhancements'.  These are usually designed to reduce visible flaws, improve the colour or stabilise faults.  Many of these techniques are near impossible to detect in the secondary market without advanced (and expensive) tests.  A GIA certification should reveal such treatments but will lead to a significant increase in price for the item.

Common enhancements include:

Laser Drilling: An industrial laser is used to create microscopic holes down to black carbon inclusions.  Acid is then used to 'bleach' the inclusions and reduce their visibility.  The tiny holes created by this process can often be seen using a high power microscope.

Fracture Filling:  Using specialist types of glass or silicones to fill in natural fractures and faults within the diamond.  There are a number of techniques and processes used and this type of treatment is generally applied to larger stones.  Fracture filling can often be detected under the microscope, although this may be much harder on mounted gems.

Irradiation: Diamonds can be bombarded by sub atomic particles to permanently alter their colour.  This is most commonly used to create 'fancy' colour diamonds (ie non-white).  It requires advanced equipment to detect.

Coatings: Coatings of various forms can be applied, often to try and improve the colour of diamonds (move them nearer to the colourless end of the spectrum).  These can be near impossible to detect outside of specialist labs. 

Backings: Some antique diamonds set in jewellery would have a metal foil coating applied to the backs to enhance their sparkle, this process is not considered detractive and can be a good confirmation of antique origin and increase the value of the jewellery.

High-Pressure High-Temperature Treatment (HPHT): The HPHT process, not developed until 1999, is used to alter the colour of diamonds.  It is most commonly used to alter certain types of high quality diamonds which just suffer from poor (brown/yellow) tints but are otherwise good.  It can also be used to enhance the colour of 'fancy' coloured diamonds.  Detecting HPHT treatment is usually only possible at advanced labs with specialist equipment.


Lab Grown Diamonds

Many alternatives to diamonds exist, but lab grown diamonds have only recently come to market in significant numbers.  Lab grown diamonds are real diamonds, test as diamond and have the same chemical composition.  They are still relatively expensive and are sometimes seen as more environmentally friendly and ethically sound than mined stones.  Two processes are currently available:

Chemical Vapour Deposition (CVD): The CVD process involves the use of a mixture of hydrocarbon gas and hydrogen. These chemicals are introduced into a chamber where a diamond "seed" is placed. The chamber is then subjected to high temperatures and low pressures, creating an environment conducive to diamond growth. Over time, carbon atoms from the gas mixture adhere to the diamond seed, layer by layer, resulting in the growth of a the diamond.  This process was not commercially viable until the 2000's so they are relatively scarce on the secondary market.

High-Pressure High-Temperature Process (HPHT): The HPHT diamond process aims to replicate the natural conditions under which diamonds are formed deep within the Earth. By subjecting a small diamond seed to intense pressure and high temperatures, scientists are able to stimulate the growth of a larger diamond crystal.  This process was developed in the 1950's but HPHT diamonds have not been available in commercial quantity until the late 1990's.  They are still relatively expensive and scarce due to the large amount of energy and specialist equipment needed to produce them, but incremental advancements are beginning to see larger numbers enter the market.

Diamond Simulants

Simulated diamonds are not genuine diamonds, but alternative gems which have a similar look.  They can be man made or natural, but they will not test as diamond and have a much lower value.

Natural simulants include:

  • Clear Sapphire
  • Clear Spinel
  • Clear Topaz
  • Clear Quartz
  • Clear Zircon

Man made simulants include

  • Lab grown sapphire
  • Lab grown spinel
  • Lab grown quartz
  • High dispersion glass (eg Swarovski Crystal)
  • Cubic Zirconia (CZ)
  • Strontium Titanate
  • Yttrium Aluminium Garnet (YAG)
  • Gadolinium Gallium Garnet (GGG)
  • Moissanite

From of the above list moissanite and cz gems have the closest look to genuine diamonds, with both exhibiting more 'fire' than a genuine diamond.  For general jewellery use only an expert is likely to be able to tell the difference without very close inspection.  CZ's in particular are excellent for showy jewellery at very reasonable cost.

As long as you understand what you are purchasing there is no problem with buying jewellery with simulated diamonds at the appropriate price.


Trade Names for Man Made & Diamond Simulants

Many trade names for man made and simulated diamonds are used as marketing spiel to attract buyers.  Some retailers are upfront about what you will be getting, others head towards the territory of deception, especially on internet sales platforms such as Etsy.  Sellers on online platforms can mis label simulants as lab created - most commonly cz is listed as lab created when it is actually a simulant. 

Please take care not to make an expensive mistake, at Blue Cherry Antiques we are careful never to mislead over the origin of a gemstone.  Below is a compilation of trade names we come across for 'diamonds' which are not diamonds at all.  This list will be updated as we find new examples, readers are encouraged to email us with new ones they come across especially deceptive types on online sales platforms.


Above Ground Diamonds - Marketing term for general man made diamonds

Amora Gem or Amora Diamond - Trade name for moissanite

Asha Diamond - A proprietory coated cubic zirconia

Diagem - Trade name for strontium titanate 

Diamondesque - Trade name for cubic zirconia

Diamonique - QVC's trade name for cubic zirconia

Djevalite - Original name for cubic zirconia

Fabulite - Trade name for strontium titanate

Fianite - Old trade name for cubic zirconia

Forever One - Trade name for moissanite

Harro Gem - Trade name for moissanite

Marvelite - Trade name for strontium titanate

Nexus Diamond - Proprietary coated cubic zirconia

Pink Ice - Marketing name for pink cubic zirconia

Signity Diamond or Signity Star Stone - Trade name for cubic zirconia

Silver Crystal - Swarovski's trade name for their proprietary lead glass formula

Supernova - Trade name for moissanite