The 4Cs

When it comes to defining the quality of a diamond, you must consider the 4Cs: Cut, Colour, Clarity and Carat weight. This criteria helps describe the quality of a mined or lab-grown diamond, and therefore determines its value. Each category has precise definitions set by IGI. All Diamond Library diamonds come with an IGI certificate which outlines all 4Cs.


A diamond's cut is arguably the most critical factor to consider when buying a diamond. Why? It's because the cut contributes sharply in giving the diamond its sparkle. If a diamond is cut too shallow or too deep, it can lose its play on light.

Diamond Cut Table Size

Diamond Quality


Note to self: always refer to the lack of the diamond's colour when grading its whiteness. The highest quality diamonds are colourless, which can be graded from a scale of D to Z. D represents a colourless diamond and Z refers to a light yellow or brown colour. At the Diamond Library, we carry K+ coloured diamonds that provide abundant radiance.

Invisible To The Naked Eye!K+
  • Exc, White Exc, White D E F
  • Rare White Rare White G H
  • White White I J K
  • Slightly White Slightly White I M
  • Tinted White Tinted White N O P Q R
  • Tinted Colour Tinted Colour S T U V W X Y Z


A diamond's clarity refers to imperfections found on the surface or internally. Internal flaws are called inclusions, while external imperfections are referred to as blemishes. The majority of diamonds, both mined and lab-grown, feature inclusions and blemishes on a microscopic scale, which is why even diamonds with the highest clarity grade feature slight inclusions. At the Diamond Library, we reject 60% of all gem-grade diamonds, which is a level above the average. The minor inclusions featured in our lab-grown diamonds are entirely invisible to the naked eye.

  • Slightly
    Slightly Included SI1
  • Very Slightly
    Very Slightly Included VS1
  • Very Very Slightly
    Very Very Slightly Included VVS1
  • Internally
    Internally Flawless IF
  • Flawless
    Flawless FL


A Carat refers to a diamond's weight and gives you a sense of its size. The unit of weight for diamonds is the metric carat, which is one-fifth of a gram and is divided into 100 points. A bigger diamond doesn't always mean a more expensive one — you have to consider all the 4 Cs. Here's a tip: When you compare diamond carat sizes, consider a diamond's cut. A high-carat diamond with a poor cut grade can look smaller, often featuring a deeper cut. On the other hand, a diamond with a smaller carat and a sharper cut is always preferable.

  • .25 CT (4.1 MM) .25 CT
    (4.1 MM)
  • .5 CT (5.1 MM) .5 CT
    (5.1 MM)
  • .75 CT (5.8 MM) .75 CT
    (5.8 MM)
  • .1 CT (6.4 MM) .1 CT
    (6.4 MM)
  • 1.25 CT (6.9 MM) 1.25 CT
    (6.9 MM)
  • 1.5 CT (7.4 MM) 1.5 CT
    (7.4 MM)
  • 1.75 CT (7.8 MM) 1.75 CT
    (7.8 MM)
  • 2 CT+ (8.1 MM) 2 CT+
    (8.1 MM)

Find Your Shine

All our diamonds are ethically sourced, lab-grown and conflict-free.