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Diamond School

January 28, 2022 4 min read

Welcome to Diamond School

The McGuire Diamonds guide to what are quite possibly the worlds most ancient and beautiful materials. The 4 C's were created to explain the value and appearance of a diamond. Empower yourself with knowledge.

Diamond shapes learn about diamonds


The first of the 4 C's that we are going to look at is cut. When it comes to diamond grading or certification cut refers to how well the diamond is made. You will see this reference in the 'anatomy' section below. Think of a diamond as an arrangement of tiny angled mirrors. A standard round brilliant cut diamond has 57 or 58 of them – what gemologists call “facets.” These facets reflect light off of each other, bounce light into the diamond, break up the light into a spectrum of colours, and return light back up to your eye. Cut quality is the factor that fuels a diamond’s fire, sparkle and brilliance. The allure and beauty of a particular diamond depends more on cut quality than anything else. A diamond with an excellent cut grade is very bright. It shows an even pattern with good contrast between light and dark areas, so the reflections appear crisp and well-balanced. This tells you that the cutter made the best possible use of the rough stone. A good cut grade diamond isn’t quite as bright – reflections aren’t as sharp and there’s more darkness or dullness in the diamond. A poor cut grade diamond has much more prominent dark areas or dullness. Given the choice, most people would pick either excellent or very good cut diamonds. We always put priority on finding the best cut grade for your budget. 

Diamond education diamond cut grades


Diamond colour is all about what you can’t see. Diamonds are valued by how closely they approach colourlessness – the less colour, the higher their value (the exception to this is fancy colour diamonds, such as pinks and blues, which lie outside this colour range). The most common diamonds run from colourless to near-colourless. The colour scale begins with the letter D, representing colourless, and continues with increasing presence of colour to the letter Z, which would be a light yellow or brown shade. Each letter grade has a clearly defined range of colour appearance. Diamonds are colour-graded by comparing them to stones of known colour under controlled lighting and precise viewing conditions.

Diamond colour guide diamond school


Diamonds form deep within the earth, under extreme heat and pressure, because of this they often contain unique birthmarks, either internal (inclusions) or external (blemishes).  Diamond clarity refers to the absence of these inclusions and blemishes. Diamonds without these birthmarks are rare, and rarity affects a diamond’s value. Diamonds are assigned a clarity grade that ranges from flawless (FL) to diamonds with obvious inclusions (I3). When it comes to cost, diamond clarity has a major impact on the cost of a stone.

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


Diamond carat (ct) refers to the weight of a stone and not the size, this is a particularly important to know when shopping for a diamond. Just as a euro is divided into 100 cents, a carat is divided into 100 points. For example, a 50-point diamond weighs 0.50 carats (ct). Two diamonds of equal weight can have very different values depending on the other members of the 4 C’s: clarity, colour and cut. All else being equal, diamond price increases with diamond carat weight because larger diamonds are rarer and more desirable. 

Diamond carat weight guide


A specific set of terms is used to describe parts of a polished diamond. Each part of a diamond makes its own contribution to the diamond’s appearance. In the standard round brilliant, there are 57 or 58 facets. The table facet, usually the largest facet on the diamond, helps gather light from above and either reflects it back to the observer or directs it into the diamond’s interior. The crown facets, consisting of 8 bezels, 8 stars, and 16 upper halves, gather and disperse light to create brightness, fire, and a scintillating pattern of light and dark. The pavilion facets, consisting of 16 lower halves, 8 mains, and an optional cullet, reflect the light back through the crown to the viewer’s eye. All of these facets work together creating each diamond’s unique appearance.

parts of a diamond

Laboratory Grown Diamonds

Lab-created diamonds consist of actual carbon atoms arranged in the characteristic diamond crystal structure. Since they are made of the same material as natural diamonds, they exhibit the same optical and chemical properties. A synthetic diamond is the result of a technological process, as opposed to the geological process that creates natural diamonds. Synthetic diamonds have essentially the same chemical composition, crystal structure, optical, and physical properties of diamonds found in nature. Most synthetic diamonds are categorised as either high-pressure, high-temperature (HPHT) or chemical vapour deposition (CVD) diamonds, depending on the method of their production. Since HPHT and CVD diamonds are virtually identical to natural diamonds, differences only become clear when they are analysed in a gem laboratory. Lab-created diamonds and earth-created diamonds offer identical optical and chemical composition. The sparkle is the same - the core difference between them is their origin. Because of the ever growing popularity of these lab created stones, diamond certification has never been more important. All Lab and Earth (natural) diamonds that we supply are certified and laser engraved on the girdle of each stone with a unique certification number. Certification will show that a stone is natural or Earth created v's Lab-created.